api: make readiness and prometheus port configurable

[zirain]

xref: #5144

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.86%. Comparing base (fcc458a) to head (34f58c9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5193      +/-   ##
==========================================
- Coverage   66.88%   66.86%   -0.02%     
==========================================
  Files         210      210              
  Lines       32998    32998              
==========================================
- Hits        22070    22065       -5     
- Misses       9589     9594       +5     
  Partials     1339     1339              

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