feat(prowler): chunk9 add the GCP base contract (#422)

[Christophe Melchior (Kakudou)]

Part of #422.

Chunk 9 of the Prowler injector stack: add the GCP base contract — the CHK009 base GCP provider: the BDD suite (behaviour, OCSF status / lifecycle logs / verbose diagnostics / OCSF capture fixtures), the contracts/gcp.py GCP contract module, its registration in the registry / __init__ (GCP joins AWS and Azure as an executable contract), the quality-gate pass, and the final OCSF capture alignment — including the cross-chunk BDD updates (chk001, chk007, chk008) and the chk006 unit registry expectations.

Re-landed from feat/422-prowler-chk009-base-gcp-provider (56db1f7..c9aed54): 7 source commits folded into 2 (I1: 9671004 + 3 fixture-alignment folds; I2: d3c905f + af90ee5 + c9aed54 — every cherry-pick applied clean, zero conflicts). Gate V (whole-branch tree vs source tip c9aed54): byte-identical except (a) the 14 pyproject.toml version differences of the other injectors (base move to 3.260821.0; prowler/ untouched), (b) the 6 trap-analysis.md files excluded by standing call (5 carried from earlier chunks + the new chk009 one), and (c) one approved deviation — the pinned pyoaev version assert removed from prowler/tests/unit/chk006_executable_base/test_outputs_registry_runtime.py.

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 1 line in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
prowler/prowler/contracts/gcp.py	94.73%	1 Missing ⚠️

Additional details and impacted files

@@                              Coverage Diff                              @@
##           feat/422-prowler-injector-chk8-base-azure     #439      +/-   ##
=============================================================================
+ Coverage                                      84.87%   84.90%   +0.02%     
=============================================================================
  Files                                            188      189       +1     
  Lines                                           8100     8121      +21     
=============================================================================
+ Hits                                            6875     6895      +20     
- Misses                                          1225     1226       +1     

Files with missing lines	Coverage Δ
prowler/prowler/contracts/__init__.py	100.00% <100.00%> (ø)
prowler/prowler/contracts/registry.py	93.75% <100.00%> (+0.13%)	⬆️
prowler/prowler/contracts/gcp.py	94.73% <94.73%> (ø)

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