Enable promlinter and enhance exposed metrics.

[kanuahs]

Description

Which issue(s) this PR fixes:

Fixes #

Testing

Checklist:

• I ran tests as well as code linting locally to verify my changes.
• I have done manual verification of my changes, changes working as expected.
• I have added new tests to cover my changes.
• My changes follow contributing guidelines of Fission.
• I have signed all of my commits.

[codecov]

Codecov Report

Merging #2550 (ed9de69) into main (dc4c6e2) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2550   +/-   ##
=======================================
  Coverage   18.78%   18.78%           
=======================================
  Files          62       62           
  Lines        6766     6766           
=======================================
  Hits         1271     1271           
  Misses       5393     5393           
  Partials      102      102           

Flag	Coverage Δ
unittests	18.78% <ø> (ø)

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