Test bash shell on Windows for CodeQL query unit tests

[Copilot]

What This PR Contributes

Tests whether Windows CodeQL test failures are caused by shell/path differences by migrating the Windows workflow from PowerShell/CMD to bash.

• Workflow shell migration: All run steps in ql-unit-tests-windows.yml now use shell: bash
  • CodeQL CLI setup and installation
  • QL pack installation
  • Node.js and npm verification
  • Test execution
• CDS compilation: Switched from cds-compilation-for-actions.cmd to cds-compilation-for-actions.sh
• Error handling improvements:
  • Portable JSON parsing using sed instead of grep -P
  • Explicit error handling for download/extraction failures
  • Process substitution for reliable variable scoping in loops

Hypothesis

The two failing Windows tests (HandlerParameterOfExposedService.ql and remoteflowsource.ql) expect forward-slash paths (e.g., srv/service1.js) but PowerShell produces backslash paths. Bash normalizes to forward slashes on all platforms.

Trade-offs

Git Bash is available by default on windows-latest runners but not guaranteed on arbitrary Windows systems. This is acceptable for CI/CD purposes.

Future Works

• If successful, this becomes a temporary workaround until proper Windows path handling is implemented in CodeQL test infrastructure
• If unsuccessful, investigate CodeQL CLI's path normalization behavior on Windows

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