GH-51335: [CI][MATLAB] Fix Windows post-cache file locking and Debian pipx upgrade error

[Diveyam-Mishra]

Rationale for this change

Resolves #51335.

Two deterministic CI errors cause confusion across PRs:

1. AMD64 Windows 2022 MATLAB fails in post-job cache hashing (hashFiles('cpp/', 'matlab/') failed) because background MSVC compiler processes (mspdbsrv.exe, �ctip.exe) remain running with exclusive file handles open on generated files under cpp/.
2. AMD64 Debian SIMD Level NONE fails during docker build because install_gcs_testbench.sh runs pip install -U pipx against Debian's apt-managed pipx package which lacks a RECORD file, triggering pip 24+'s error: uninstall-no-record-file.

What changes are included in this PR?

1. Add a cleanup step in .github/workflows/matlab.yml with if: always() to terminate lingering MSVC compiler daemons (mspdbsrv.exe and �ctip.exe) before post-job caching steps run.
2. Add --ignore-installed to pip install -U pipx in ci/scripts/install_gcs_testbench.sh to allow upgrading pipx over apt-installed packages safely.

Are these changes tested?

Yes, via CI.

Are there any user-facing changes?

No.

• GitHub Issue: [MATLAB][CI] Fix deterministic CI failures in Windows MATLAB, and Debian #51335

[github-actions]

⚠️ GitHub issue #51335 has been automatically assigned in GitHub to PR creator.

[Copilot]

🟢 Approval recommended

No unresolved review comments remain, and all reviewers assessed it as ready.

Pull request overview

Fixes two deterministic CI failures involving Windows MATLAB file locking and Debian pipx upgrades.

Changes:

• Cleans up lingering MSVC processes before cache finalization.
• Adds --ignore-installed when upgrading pipx.

File summaries

File	Summary
ci/scripts/install_gcs_testbench.sh	Prevents Debian pipx uninstall metadata errors.
.github/workflows/matlab.yml	Adds unconditional Windows compiler-process cleanup.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Lite

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[raulcd]

The Matlab job is still failing on this PR.
Could you split those into two issues instead of grouping unrelated issues?
I'd like to merge the fix for gcs_testbench.sh to fix several nightly CI failures, let us know if you can do that on a separate PR.

[raulcd]

The install_gcs_testbench issue has been fixed on a separate issue in order to fix several CI failures. Thanks for raising this one, let's repurpose it and focus only on the matlab issue.

• [CI][Docs] debian-cpp job fails on pip install packaging #51345