feat(deployment)!: move security contexts into the deployment dict

`podSecurityContext` and `containerSecurityContext` are both Deployment-scoped: the former is rendered into
`spec.template.spec.securityContext`, the latter into the securityContext of the Gitea container and the
chart-managed init containers. Keeping them at the top level hid that pod/container distinction behind a
naming convention and separated them from the other pod- and container-scoped settings that already live
under `deployment` and `deployment.gitea`.

`podSecurityContext` therefore becomes `deployment.securityContext` and `containerSecurityContext` becomes
`deployment.gitea.securityContext`, which makes the scope obvious from the values path alone and continues
the consolidation started with `deployment.gitea.env`, `deployment.gitea.resources` and
`deployment.gitea.image`.

The template helpers keep their argument-based signatures, because `gitea.containerSecurityContext` is also
used by the Helm test pod and is not bound to a single values path.

Both removed keys are covered by the deprecation check so that a silently dropped security context cannot
lead to containers unexpectedly running as root or without the configured capability set.

BREAKING CHANGE: `podSecurityContext` and `containerSecurityContext` no longer exist. Use
`deployment.securityContext` and `deployment.gitea.securityContext` instead. Installations that still set
the old keys will fail to render unless `checkDeprecation` is set to `false`.

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

templates/gitea/deployment.yaml

@@ -62,9 +62,9 @@ spec:
         {{- end }}
     spec:
       {{- $hostUsers := include "gitea.hostUsers" . | trim }}
-      {{- $podSecurityContext := include "gitea.podSecurityContext" . | trim }}
-      {{- $containerSecurityContext := include "gitea.containerSecurityContext" (list . (deepCopy .Values.containerSecurityContext)) | trim }}
-      {{- $commandInitContainerSecurityContext := include "gitea.commandInitContainerSecurityContext" (list . (deepCopy .Values.containerSecurityContext)) | trim }}
+      {{- $securityContext := include "gitea.deployment.securityContext" . | trim }}
+      {{- $containerSecurityContext := include "gitea.containerSecurityContext" (list . (deepCopy .Values.deployment.gitea.securityContext)) | trim }}
+      {{- $commandInitContainerSecurityContext := include "gitea.commandInitContainerSecurityContext" (list . (deepCopy .Values.deployment.gitea.securityContext)) | trim }}
       {{- $runtimeContainerSecurityContext := include "gitea.runtimeContainerSecurityContext" . | trim }}
       {{- if .Values.deployment.schedulerName }}
       schedulerName: "{{ .Values.deployment.schedulerName }}"
@@ -79,9 +79,9 @@ spec:
       hostUsers: {{ $hostUsers }}
       {{- end }}
       {{- include "gitea.images.pullSecrets" . | nindent 6 }}
-      {{- if $podSecurityContext }}
+      {{- if $securityContext }}
       securityContext:
-        {{- $podSecurityContext | nindent 8 }}
+        {{- $securityContext | nindent 8 }}
       {{- end }}
       initContainers:
         {{- if .Values.preExtraInitContainers }}