Fix implicit optional types

[jacobtomlinson]

Continuing on the path of #381 this PR runs no_implicit_optional on kr8s to add missing Optional types.

This removes around 70 mypy warnings and leaves us with 252.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.35%. Comparing base (87063fc) to head (5bb2cd7).
Report is 116 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #411      +/-   ##
==========================================
+ Coverage   94.61%   95.35%   +0.73%     
==========================================
  Files          29       29              
  Lines        3141     3619     +478     
==========================================
+ Hits         2972     3451     +479     
+ Misses        169      168       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.