Run hammer against MySQL in CI

[mhutchinson]

This ensures a basic level of write performance. It isn't a perfect performance benchmark because the job could be run on different specs of machine, but it's a first foray into getting the hammer running in CI.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.02%. Comparing base (46ec9c2) to head (ba9998f).
Report is 60 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #142      +/-   ##
==========================================
+ Coverage   35.80%   36.02%   +0.22%     
==========================================
  Files          16       33      +17     
  Lines        1363     2823    +1460     
==========================================
+ Hits          488     1017     +529     
- Misses        801     1696     +895     
- Partials       74      110      +36     

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