Rewrite CRDB pool retry tests to use synctest

[ivanauth]

Summary

Rewrites the CRDB pool retry tests to use Go's testing/synctest package for better time simulation and test reliability.

Fixes #2713

Changes

• Wrap all retry tests in synctest.Test(t, func(t *testing.T) { ... })
• Use t.Context() instead of context.Background()
• Add t.Parallel() for concurrent test execution
• Rename BuildMemoryUsageProvider to MustBuildMemoryUsageProvider for consistency

Benefits

• Tests no longer rely on real time delays
• More deterministic test execution
• Faster test runs with simulated time
• Better parallel execution support

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 77.63%. Comparing base (ae83447) to head (483cf87). :warning: Report is 20 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2754      +/-   ##
==========================================
+ Coverage   77.03%   77.63%   +0.61%     
==========================================
  Files         466      471       +5     
  Lines       49199    49564     +365     
==========================================
+ Hits        37896    38475     +579     
+ Misses       8514     8248     -266     
- Partials     2789     2841      +52     

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