Standardize Kubernetes API flag name

[micahhausler]

Description

Kubernetes auto-injects certain environment variables into pods for service discovery, and the KUBERNETES env var is defined for all pods in all namespaces with the service IP of the API server. Because we already support viper environment variable mappings for flags, changing the flag name here will automatically support the in-cluster Kubernetes client configuration

[codecov]

Codecov Report

Merging #619 (fee17e4) into main (c9ebfa8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #619   +/-   ##
=======================================
  Coverage   44.65%   44.65%           
=======================================
  Files          61       61           
  Lines        3509     3509           
=======================================
  Hits         1567     1567           
  Misses       1860     1860           
  Partials       82       82           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c9ebfa8...fee17e4. Read the comment docs.