test: wait for cache test server to listen

[trivikr]

This relates to...

Fixes: #5199

Rationale

The cache test worker imports the upstream cache-tests server fixture, but that fixture can finish module evaluation before the server is actually listening. Until the upstream fixture exposes or awaits server readiness, the worker should wait for the configured BASE_URL to accept connections before running the suite.

Changes

• Wait for the cache test server to listen before starting the cache test suite.
• Add a TODO linking the upstream cache-tests issue so this workaround can be removed once fixed upstream.

Features

N/A

Bug Fixes

N/A

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

Assisted-by: openai:gpt-5.5

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.27%. Comparing base (4f8f814) to head (de44170).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5242   +/-   ##
=======================================
  Coverage   93.27%   93.27%           
=======================================
  Files         110      110           
  Lines       36366    36366           
=======================================
  Hits        33922    33922           
  Misses       2444     2444           

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[mcollina]

lgtm