feat(appset): Add argocd.argoproj.io/application-set-name to rendered appset applications

[MeNsaaH]

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As part of #13309, this PR adds a new label to all applications generated by appsets. This way, we can list all the apps belonging to an appset by running

argocd app list -l argocd.argoproj.io/appset-instance=app-set-name

closes #13309

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.09 ⚠️

Comparison is base (56d1733) 49.15% compared to head (62a08fd) 49.07%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #13456      +/-   ##
==========================================
- Coverage   49.15%   49.07%   -0.09%     
==========================================
  Files         248      250       +2     
  Lines       42902    43248     +346     
==========================================
+ Hits        21090    21225     +135     
- Misses      19694    19892     +198     
- Partials     2118     2131      +13     

Impacted Files	Coverage Δ
...cationset/controllers/applicationset_controller.go	62.72% <100.00%> (-0.66%)	⬇️

... and 38 files with indirect coverage changes

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[blakepettersson]

This looks reasonable for me at least, at $dayjob we currently work around this by setting our own custom label. Let's see if my sentiment is shared by the others 😄

[crenshaw-dev]

Thanks, @MeNsaaH!

[dyatlov]

This PR introduced a regression: #15282
It is no longer possible to have ApplicationSets with names longer than 63 chars.

I don't think forcing a custom label for an application was a good idea in the first place, honestly:

1. because of the issue above
2. because ApplicationSet is not creating applications synchronously and argocd app list -l argocd.argoproj.io/appset-instance=app-set-name (or its API analogue) can provide an incomplete view (especially if part of the applications are created and another part are not - which is the case for the issue above)

A better approach is to add wanna-be generated application names into ApplicationSet resource itself.
A much better approach is to also include application sync statuses next to application names within a given ApplicationSet.