feat: Add generic/external jwt authentication (Alpha)

[bgrouxupgrade]

Closes #14250
Based on: #20928, #22901
Feature implemented by @wrmedford
Contributions by @alexander-applyinnovations

This allows for generic JWTs to be used for authentication that are minted outside of Argo. Argo currently mints its own JWTs for auth outside of Dex, and this extends its capabilities to utilize JWTs that originate from Identity Aware Proxies.

PR structure;

• Initial commit (squashed from previous PRs)
• Follow on commits for additional features (signing method, groups/nested supports, fixes)
• Commit to address most initial PR comments
• Commits to address structural comments

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).
• The title of the PR conforms to the Title of the PR
• I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• 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.
• I have signed off all my commits as required by DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My build is green (troubleshooting builds).
• My new feature complies with the feature status guidelines.
• I have added a brief description of why this PR is necessary and/or what this PR solves.
• Optional. My organization is added to USERS.md.
• Optional. For bug fixes, I've indicated what older releases this fix should be cherry-picked into (this may or may not happen depending on risk/complexity).

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[codecov]

Codecov Report

❌ Patch coverage is 60.21127% with 113 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@48c969b). Learn more about missing BASE report.
⚠️ Report is 95 commits behind head on master.

Files with missing lines	Patch %	Lines
util/session/sessionmanager.go	51.38%	24 Missing and 11 partials ⚠️
util/jwt/token/external.go	72.26%	17 Missing and 16 partials ⚠️
util/jwt/jwt.go	51.35%	17 Missing and 1 partial ⚠️
server/server.go	14.28%	12 Missing ⚠️
cmd/argocd/commands/project_role.go	0.00%	9 Missing ⚠️
server/logout/logout.go	0.00%	1 Missing and 1 partial ⚠️
util/oidc/oidc.go	50.00%	2 Missing ⚠️
util/oidc/provider.go	71.42%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #25567   +/-   ##
=========================================
  Coverage          ?   62.52%           
=========================================
  Files             ?      354           
  Lines             ?    50258           
  Branches          ?        0           
=========================================
  Hits              ?    31425           
  Misses            ?    15800           
  Partials          ?     3033           

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[bgrouxupgrade]

Not super happy with the util/jwt/token package being added but there's a nasty import cycle because we need settings in here which imports a ton of things and the util/jwt package is used is a ton places some of which are imported by settings ... it was either this or push settings behind an interface local to the jwt package which felt even uglier ¯\_(ツ)_/¯