Update conftest and test_cmoriser_integration for om2 mock config

[rhaegar325]

Summary

This PR fixes a failing integration test related to processing multiple ocean variables using ACCESS_ESM_CMORiser.

What was changed

• Updated test_cmoriser_integration.py
• Added mock_config_om2 fixture to conftest.py
  • Provides a standardized ACCESS-OM2 configuration for reusable test setup

Bug Fix

Previously, the integration test passed an incomplete configuration, which caused incorrect CMOR variable mapping when using compound names. With the new fixture and corrected patch logic, the expected CMOR variable (tos from Omon.tos) is now properly validated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.44%. Comparing base (a4f53c8) to head (7960647).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #138      +/-   ##
==========================================
+ Coverage   57.06%   57.44%   +0.37%     
==========================================
  Files          18       18              
  Lines        2399     2399              
==========================================
+ Hits         1369     1378       +9     
+ Misses       1030     1021       -9     

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