Add `install-source` label to Operator deployment

[chrismuellner]

Description

Any value for platform is now allowed, with the default assumption that manifests for kubernetes are generated.

• Manifest and Olm are set as install-source if helm is run with those values
• Any other platform is assumed as special marketplace and passed to the label without modification
• Helm is the default value, if nothing else matches

K8S-10736

How can this be tested?

• Run make test/helm
• Try out different values for platform and check the resulting manifests are for the right platform and the label is set correctly

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 64.54%. Comparing base (6446a2d) to head (bbb1c07). Report is 1 commits behind head on main.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3628   +/-   ##
=======================================
  Coverage   64.54%   64.54%           
=======================================
  Files         399      399           
  Lines       21401    21401           
=======================================
  Hits        13814    13814           
  Misses       6264     6264           
  Partials     1323     1323           

Flag	Coverage Δ
unittests	64.54% <ø> (ø)

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