CI/CD: Cache server Docker image to speed up time for setting up server

[juliannguyen4]

Manual testing:

• Build artifacts can reuse cache from the same branch
• tests.yml can reuse cache from the same ref for PRs

TODO

• Cache works for manylinux_x86_64 and macosx_arm64, but not manylinux_aarch64

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.78%. Comparing base (ce5e01a) to head (e41840e).
Report is 3 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #743   +/-   ##
=======================================
  Coverage   81.78%   81.78%           
=======================================
  Files          99       99           
  Lines       14552    14552           
=======================================
  Hits        11901    11901           
  Misses       2651     2651           

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[juliannguyen4]

#855 We switched to using a bash script to setup the server instead of building a server Docker image with additional features. So this no longer applies