[CECO-455] [kubectl-eds plugin] diff command

[tbavelier]

What does this PR do?

• This PR introduces a diff command in the kubectl-eds plugin to do the diff between the canary and the active ExtendedReplicaSets spec

Motivation

• https://datadoghq.atlassian.net/browse/CECO-455

[celenechang]

i'm going to remove the skip-qa label because i think this will beed to be part of the next release

[codecov-commenter]

Codecov Report

Merging #168 (834abed) into main (20c7885) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #168   +/-   ##
=======================================
  Coverage   63.22%   63.22%           
=======================================
  Files          41       41           
  Lines        3073     3073           
=======================================
  Hits         1943     1943           
  Misses       1014     1014           
  Partials      116      116           

Flag	Coverage Δ
unittests	63.22% <ø> (ø)

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