feat: equality-based and set-based filtering by label keys and values for list, sync, delete and wait App commands (#10548)

[maheshbaliga]

This PR resolves the -l / --selector flag part of the issue #10548 , where apps can be filtered with theirs labels and values. It achieves feature-parity with kubectl.

List, Sync, Delete and Wait commands to manage applications can now be filtered by label keys and values. Matching apps must satisfy all of the specified label constraints, though they may have additional labels as well. Equality-based operators allowed are =, == and !=. Set-based operators allowed are exists, not exists, in & notin.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
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• I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• Does this PR require documentation updates?
• I've updated documentation as required by this PR.
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• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
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[codecov]

Codecov Report

Base: 45.65% // Head: 45.68% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (5d835dd) compared to base (11c44f2).
Patch coverage: 12.50% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10729      +/-   ##
==========================================
+ Coverage   45.65%   45.68%   +0.02%     
==========================================
  Files         236      236              
  Lines       28702    28706       +4     
==========================================
+ Hits        13104    13113       +9     
+ Misses      13804    13800       -4     
+ Partials     1794     1793       -1     

Impacted Files	Coverage Δ
cmd/argocd/commands/app.go	18.50% <0.00%> (-0.20%)	⬇️
server/application/application.go	28.98% <100.00%> (+1.05%)	⬆️
util/settings/settings.go	51.36% <0.00%> (ø)

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[crenshaw-dev]

This is awesome, @maheshbaliga!

Could you add examples to each of the commands' Example text?

Also, would you have time to implement the same improvement for the argocd app delete command? I just merged -l support for that command.

[maheshbaliga]

@crenshaw-dev, thank you for the review. The examples have been added for List, Sync, Delete & Wait commands. Also, I pulled the label selector changes made to the Delete command and tested it with my code changes. This filtering logic works with Delete command too, since this flow also invokes the List() in application.go.

[crenshaw-dev]

Thanks @maheshbaliga!