test: include cache-test worker metadata on failure

[trivikr]

This relates to...

Refs: #5199

Rationale

When a cache-test worker exits before printing its own summary, the parent process currently only reports Process completed with exit code 1. This makes it hard to identify which cache environment failed.

Changes

• Include cache-test worker metadata on failure: port, cache store, cache type, exit code, and signal.
• Capture child process spawn errors in the worker’s buffered output.

Features

N/A

Bug Fixes

Include cache-test worker metadata on failure

Breaking Changes and Deprecations

N/A

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• Documented
• Review ready
• In review
• Merge ready

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.27%. Comparing base (296b424) to head (b589430).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5276   +/-   ##
=======================================
  Coverage   93.27%   93.27%           
=======================================
  Files         110      110           
  Lines       36384    36384           
=======================================
  Hits        33938    33938           
  Misses       2446     2446           

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