refactor(templates)!: centralize Secret names in gitea.secret.*.name helpers

The names of the Secrets rendered by the chart were built inline in each template and, for two of
them, in ad-hoc chart-wide helpers. The same name therefore existed in several places (Deployment
volumes, ServiceMonitor credentials, the Secret templates themselves), which made every rename a
multi-file change and allowed the references to drift apart unnoticed - the Helm unit tests render
one template at a time and cannot detect a mismatching secretName.

All Secret names are now defined once in templates/gitea/_secrets.tpl:

  gitea.secret.config.name        -> <fullname>-config
  gitea.secret.gpg.name           -> <fullname>-gpg-key (or signing.existingSecret)
  gitea.secret.init.name          -> <fullname>-init
  gitea.secret.inlineConfig.name  -> <fullname>-inline-config
  gitea.secret.metrics.name       -> <fullname>-metrics

gitea.gpg-key-secret-name and gitea.metrics-secret-name are removed from _helpers.tpl accordingly.

A checksum/inlineConfig pod annotation is added as well. After the inline configuration had been
split out of secret_config.yaml, changes to it were no longer covered by any checksum annotation and
did not trigger a rollout of the Deployment.

Finally the metadata attributes of the Secret templates are sorted alphabetically as required by the
chart conventions.

BREAKING CHANGE: two Secrets are renamed. The config Secret changes from <fullname> to
<fullname>-config and the metrics Secret from <fullname>-metrics-secret to <fullname>-metrics. Helm
replaces both on upgrade; references to them from outside the chart have to be adjusted.

Co-authored-by: Copilot <copilot@github.com>

unittests/helm/deployment/deployment-additional-config.yaml

@@ -5,6 +5,7 @@ release:
 templates:
   - templates/gitea/deployment.yaml
   - templates/gitea/secret_config.yaml
+  - templates/gitea/secret_inlineConfig.yaml
 tests:
   - it: Renders a deployment
     template: templates/gitea/deployment.yaml