feat: add Gitlab PR generator webhooks support

[Enity]

Closes #10234

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[codecov]

Codecov Report

Merging #10235 (a069a0f) into master (84bb996) will increase coverage by 0.24%.
The diff coverage is 52.45%.

@@            Coverage Diff             @@
##           master   #10235      +/-   ##
==========================================
+ Coverage   45.93%   46.18%   +0.24%     
==========================================
  Files         227      226       -1     
  Lines       27434    27579     +145     
==========================================
+ Hits        12603    12737     +134     
- Misses      13118    13122       +4     
- Partials     1713     1720       +7     

Impacted Files	Coverage Δ
cmd/argocd/commands/app.go	20.44% <0.00%> (-0.06%)	⬇️
controller/sync.go	55.33% <0.00%> (-0.77%)	⬇️
util/argo/managedfields/managed_fields.go	67.27% <ø> (+25.22%)	⬆️
controller/state.go	73.89% <33.33%> (-0.33%)	⬇️
applicationset/utils/webhook.go	73.29% <58.13%> (-0.94%)	⬇️
util/argo/diff/diff.go	52.41% <60.00%> (+0.20%)	⬆️
applicationset/utils/map.go	60.86% <0.00%> (-2.77%)	⬇️
applicationset/generators/matrix.go	70.73% <0.00%> (-2.25%)	⬇️
applicationset/generators/merge.go	59.04% <0.00%> (-1.96%)	⬇️
... and 9 more

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[Enity]

Tested manually on my own cluster. Works well.
Docker image from this PR: https://hub.docker.com/r/enity/argocd-gitlab-mr-hooks

[crenshaw-dev]

Almost perfect! One nitpick, plus, would you mind compressing the image? squoosh.app gets it down to 60kb from 600kb if I save it as a JPEG (which I think is fine for this use case).

[Enity]

Almost perfect! One nitpick, plus, would you mind compressing the image? squoosh.app gets it down to 60kb from 600kb if I save it as a JPEG (which I think is fine for this use case).

Picture is now 111kb, i kept it png just for consistency. Don't know why but all pictures is png.

[crenshaw-dev]

Thanks @Enity!