mysql - fix: isolate pooled connection lifecycles

[jaredwray]

Please check if the PR fulfills these requirements

• Followed the Contributing and Code of Conduct guidelines.
• Tests for the changes have been added (for bug fixes/features) with 100% code coverage.

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
mysql - fix: isolate pooled connection lifecycles

[gemini-code-assist]

Code Review

This pull request refactors the MySQL storage adapter to use reference-counted connection pool leases, allowing adapters with identical configuration options to share a pool while ensuring pools are not prematurely closed when other adapters are still using them. Feedback was provided to address a potential memory leak in the pool options serialization logic by avoiding a global strong Map for symbol identities and instead serializing symbols using their description or string representation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (dc563b6) to head (4eb5e77).

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #2012      +/-   ##
===========================================
+ Coverage   99.95%   100.00%   +0.04%     
===========================================
  Files          55        55              
  Lines        4887      4896       +9     
  Branches      779       779              
===========================================
+ Hits         4885      4896      +11     
+ Misses          2         0       -2     

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