[Nexthop][fboss2-dev] Add fboss2-dev config ptp transparent-clock CLI command

[vybhav-nexthop]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

• Adds fboss2-dev config ptp transparent-clock <enable|disable> to toggle ptpTcEnable in SwitchSettings
• Action level: HITLESS (no agent restart required):
  • SAI path: SaiSwitch.cpp:1910–1921 → switchManager().setPtpTcEnabled() + portManager().setPtpTcEnable() — in-service per-port config, no link bounce
  • BCM path: BcmSwitchSettings::setPtpTc() → BcmPtpTcMgr::enablePtpTc() / disablePtpTc() → iterates all ports calling bcm_port_timesync_config_set() and bcm_switch_control_port_set(bcmSwitchTimesyncEgressTimestampingMode) — live BCM SDK reconfiguration, no port re-init or link bounce; warm-boot state tracked via BcmWarmBootCache::ptpTcEnabled_
• Parent branch node config ptp follows the same pattern as config l2

Files

New:

• commands/config/ptp/CmdConfigPtp.{h,cpp} — parent branch node
• commands/config/ptp/transparent_clock/CmdConfigPtpTransparentClock.{h,cpp} — leaf handler
• test/config/CmdConfigPtpTransparentClockTest.cpp — unit tests (arg validation + queryClient)
• test/integration_test/ConfigPtpTest.cpp — E2E toggle + idempotency tests

Modified: CmdListConfig.cpp, cmake/CliFboss2.cmake, cmake/CliFboss2TestConfig.cmake, cmake/CliFboss2TestIntegrationTest.cmake, fboss2/BUCK, test/config/BUCK, test/integration_test/BUCK

Test plan

• Unit tests: CmdConfigPtpTransparentClockTest (arg validation, enable/disable transitions, already-enabled/already-disabled symmetric no-op cases)

213/926 Test #213: CmdConfigPtpTransparentClockTestFixture.argValidation ......   Passed    0.73 sec
214/926 Test #214: CmdConfigPtpTransparentClockTestFixture.disableWhenEnabled .   Passed    0.72 sec
215/926 Test #215: CmdConfigPtpTransparentClockTestFixture.enableWhenDisabled .   Passed    0.71 sec
216/926 Test #216: CmdConfigPtpTransparentClockTestFixture.alreadyEnabled .....   Passed    0.71 sec

• Integration test: ConfigPtpTest.ToggleTransparentClock + ConfigPtpTest.IdempotentToggle on a DUT

[----------] 2 tests from ConfigPtpTest
[ RUN      ] ConfigPtpTest.ToggleTransparentClock
[       OK ] ConfigPtpTest.ToggleTransparentClock (127 ms)
[ RUN      ] ConfigPtpTest.IdempotentToggle
[       OK ] ConfigPtpTest.IdempotentToggle (98 ms)
[----------] 2 tests from ConfigPtpTest (225 ms total)