chore: deprecate argocd-cm plugins (#8117)

[crenshaw-dev]

Related to #8117

1. The UI for an Application's details will now contain a warning if the Application appears to use an argocd-cm plugin.

   

2. The following commands log a warning when interacting with apps which use a deprecated plugin: argocd app create, argocd app get, argocd app set, argocd app unset, argocd app diff, argocd app list, argocd app sync, argocd app history, argocd app rollback, argocd app manifests, and argocd app edit. The argocd app list command additionally lists all returned apps which use a deprecated plugin.

   $ argocd app list
   WARN[0000] spec.plugin.name is set, which means this Application uses a plugin installed in the argocd-cm ConfigMap. Installing plugins via that ConfigMap is deprecated in Argo CD v2.5. Starting in Argo CD v2.6, this Application will fail to sync. Contact your Argo CD admin to make sure an upgrade plan is in place. More info: https://argo-cd.readthedocs.io/en/latest/operator-manual/upgrading/2.4-2.5/ 
   WARN[0000] The following Applications use deprecated plugins: plugin-test-app 
   NAME                    CLUSTER                         NAMESPACE  PROJECT  STATUS     HEALTH   SYNCPOLICY  CONDITIONS  REPO                                                                     PATH   TARGET
   argocd/plugin-test-app  https://kubernetes.default.svc  default    default  OutOfSync  Healthy  <none>      <none>      https://github.com/crenshaw-dev/plugin-test-app.git
   

3. The repo-server logs a warning when generating manifests for an App using a deprecated plugin.

4. The API server logs a warning whenever responding to a request which involves an App using a deprecated plugin.

[codecov]

Codecov Report

Merging #10341 (feee76b) into master (6756a5f) will decrease coverage by 0.15%.
The diff coverage is 13.84%.

@@            Coverage Diff             @@
##           master   #10341      +/-   ##
==========================================
- Coverage   46.13%   45.97%   -0.16%     
==========================================
  Files         228      228              
  Lines       27961    28073     +112     
==========================================
+ Hits        12900    12907       +7     
- Misses      13315    13410      +95     
- Partials     1746     1756      +10     

Impacted Files	Coverage Δ
cmd/argocd/commands/app.go	19.16% <0.00%> (-0.36%)	⬇️
server/application/application.go	30.22% <1.25%> (-1.91%)	⬇️
pkg/apis/application/v1alpha1/repository_types.go	68.60% <72.22%> (-0.54%)	⬇️
reposerver/repository/repository.go	64.47% <100.00%> (+0.13%)	⬆️

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[leoluz]

LGTM