test(storcli2): on-hardware e2e harness + sibling layout

[g-carre]

Summary

Adds a manual on-hardware e2e harness for the storcli2/perccli2 composition adapter (ARTESCA-17652) and reorganizes the integration harnesses so each adapter is clearly identifiable in its own sibling directory. Stacked on #73.

tests/integration/
  mdadm/      # moved: existing software-RAID (RHEL8/mdadm) harness
  storcli2/   # new: MegaRAID/PERC harness
  README.md   # documents both + cross-compile line

storcli2 harness — argument-driven

• Default (no args): read-only inventory — lists controllers, physical drives and logical volumes as markdown tables. Safe to run anywhere.
• Destructive commands require -confirm: create, add (expand), delete, and a full scenario (create → assert drive-removal unsupported → optional expand → delete).
• storcli2 can't remove drives, so the scenario exercises removal as a negative case (asserts ErrFunctionNotSupportedByImplementation) rather than mutating the array.
• The same composition serves both binaries via -binary (point it at perccli2 for PERC).

Notes / deviations from the ticket

• Layout differs from the ticket's suggested tests/e2e-storcli2/ — per request, both adapters now sit side by side under tests/integration/{mdadm,storcli2}/ for clarity.
• Scope is a superset of the ticket's read-only inventory: it keeps inventory as the default but adds opt-in destructive tasks/scenario behind -confirm, as discussed.
• Imports only pkg/implementation/... and pkg/core (not pkg/infrastructure); cross-compile line documented in the README and main.go.

Testing

go build ./..., go vet ./tests/integration/..., gofmt, and the full unit suite pass. Verified locally that the default inventory fails gracefully (no panic) when the binary is absent, and that destructive commands refuse to run without -confirm.

Note: Targets feature/storcli2-raidcontroller-composition (#73), not main, per the stack.

Issue: ARTESCA-17652

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