[202506] Fix ECMP scale formatting and per-endpoint MAC/VNI wrapping

[miatttao]

This is a manual cherry-pick of master PR sonic-net/sonic-utilities#4452 due to merge conflicts.

What I did

• Fixed show vnet routes output becoming unreadable at large ECMP scale (e.g. ~511 endpoints), where all endpoints were previously printed on a single line, causing column overflow and table misalignment.
• Extended the pretty‑print logic to wrap endpoint, mac_address, and vni together so per‑endpoint fields stay aligned at any ECMP scale.
• Updated tunnel route output to consistently include the metric field.
• Made the CLI more robust when optional fields are missing from DB entries, preventing runtime errors

How I did it

• Refactored the pretty‑print helper to:
  • Accept metric and handle per‑endpoint mac_address / vni lists.
  • Split all per‑endpoint fields by comma and wrap them in identical chunks so each row remains aligned.
• Computed row_width based on the longest element across endpoint, mac_address, and vni, ensuring wide MAC addresses don’t overflow the terminal.
• Removed the tunnel‑route special case (if len(epval) < 40) so all routes go through the same pretty‑print path for consistent behavior.
• Added and updated unit tests to validate:
  • Pretty‑print behavior directly.
  • Large‑scale MAC/VNI list scenarios.
  • CLI output for local, tunnel, and filtered route variants.

Tests added/updated:

• test_pretty_print_basic
• test_show_vnet_routes_all_basic
• test_show_vnet_routes_all_vnetname
• test_show_vnet_routes_tunnel_basic
• test_show_vnet_routes_tunnel_vnetname
• test_show_vnet_routes_local_basic
• test_show_vnet_routes_local_vnetname
• test_show_vnet_routes_tunnel_mac_vni_list (scale case)

How to verify it

Previous command output (if the output of a command-line utility has changed)

show vnet routes all

vnet name        prefix                    endpoint                                     mac address    vni    metric    status
----------------  ------------------------  -------------------------------------------  -------------  -----  --------  --------
Vnet_v6_in_v6-0  fddd:a156:a251::a6:1/128  fddd:a100:a251::a10:1,fddd:a101:a251::a10:1                                  active
                                           fddd:a102:a251::a10:1,fddd:a103:a251::a10:1
test_v4_in_v4-0  160.162.191.1/32          100.251.7.1                                                                  active
test_v4_in_v4-0  160.163.191.1/32          100.251.7.1                                                        0         active
test_v4_in_v4-0  160.164.191.1/32          100.251.7.1

show vnet routes tunnel

vnet name        prefix                    endpoint                                     mac address    vni    metric    status
----------------  ------------------------  -------------------------------------------  -------------  -----  --------  --------
Vnet_v6_in_v6-0  fddd:a156:a251::a6:1/128  fddd:a100:a251::a10:1,fddd:a101:a251::a10:1                                  active
                                           fddd:a102:a251::a10:1,fddd:a103:a251::a10:1
test_v4_in_v4-0  160.162.191.1/32          100.251.7.1                                                                  active
test_v4_in_v4-0  160.163.191.1/32          100.251.7.1                                                        0         active
test_v4_in_v4-0  160.164.191.1/32          100.251.7.1

show vnet routes tunnel <vnet_name> (previous example: test_v4_in_v4-0)

vnet name        prefix            endpoint     mac address    vni      metric  status
---------------  ----------------  -----------  -------------  -----  --------  --------
test_v4_in_v4-0  160.162.191.1/32  100.251.7.1                                  active
test_v4_in_v4-0  160.163.191.1/32  100.251.7.1                               0  active
test_v4_in_v4-0  160.164.191.1/32  100.251.7.1

New command output (if the output of a command-line utility has changed)

show vnet routes all

vnet name           prefix                    endpoint                                     mac address                          vni      metric    status
------------------  ------------------------  -------------------------------------------  -----------------------------------  -------  --------  --------
Vnet_mac_vni_scale  10.0.0.0/24               10.0.0.1,10.0.0.2                            aa:bb:cc:00:00:01,aa:bb:cc:00:00:02  100,200            active
                                              10.0.0.3,10.0.0.4                            aa:bb:cc:00:00:03,aa:bb:cc:00:00:04  300,400
                                              10.0.0.5,10.0.0.6                            aa:bb:cc:00:00:05,aa:bb:cc:00:00:06  500,600
Vnet_v6_in_v6-0     fddd:a156:a251::a6:1/128  fddd:a100:a251::a10:1,fddd:a101:a251::a10:1                                                          active
                                              fddd:a102:a251::a10:1,fddd:a103:a251::a10:1
test_v4_in_v4-0     160.162.191.1/32          100.251.7.1                                                                                          active
test_v4_in_v4-0     160.163.191.1/32          100.251.7.1                                                                                0         active
test_v4_in_v4-0     160.164.191.1/32          100.251.7.1

show vnet routes tunnel

vnet name           prefix                    endpoint                                     mac address                          vni      metric    status
------------------  ------------------------  -------------------------------------------  -----------------------------------  -------  --------  --------
Vnet_mac_vni_scale  10.0.0.0/24               10.0.0.1,10.0.0.2                            aa:bb:cc:00:00:01,aa:bb:cc:00:00:02  100,200            active
                                              10.0.0.3,10.0.0.4                            aa:bb:cc:00:00:03,aa:bb:cc:00:00:04  300,400
                                              10.0.0.5,10.0.0.6                            aa:bb:cc:00:00:05,aa:bb:cc:00:00:06  500,600
Vnet_v6_in_v6-0     fddd:a156:a251::a6:1/128  fddd:a100:a251::a10:1,fddd:a101:a251::a10:1                                                          active
                                              fddd:a102:a251::a10:1,fddd:a103:a251::a10:1
test_v4_in_v4-0     160.162.191.1/32          100.251.7.1                                                                                          active
test_v4_in_v4-0     160.163.191.1/32          100.251.7.1                                                                                0         active
test_v4_in_v4-0     160.164.191.1/32          100.251.7.1

show vnet routes tunnel <vnet_name> new example: test_v4_in_v4-0

vnet name        prefix            endpoint     mac address    vni    metric    status
---------------  ----------------  -----------  -------------  -----  --------  --------
test_v4_in_v4-0  160.162.191.1/32  100.251.7.1                                  active
test_v4_in_v4-0  160.163.191.1/32  100.251.7.1                        0         active
test_v4_in_v4-0  160.164.191.1/32  100.251.7.1

show vnet routes tunnel Vnet_mac_vni_scale (new scale case)

vnet name           prefix       endpoint           mac address                          vni      metric    status
------------------  -----------  -----------------  -----------------------------------  -------  --------  --------
Vnet_mac_vni_scale  10.0.0.0/24  10.0.0.1,10.0.0.2  aa:bb:cc:00:00:01,aa:bb:cc:00:00:02  100,200            active
                                 10.0.0.3,10.0.0.4  aa:bb:cc:00:00:03,aa:bb:cc:00:00:04  300,400
                                 10.0.0.5,10.0.0.6  aa:bb:cc:00:00:05,aa:bb:cc:00:00:06  500,600

[anish-n]

@miatttao please link the master PR in description

[miatttao]

@miatttao please link the master PR in description

Yes, linked!