feat(deployment)!: move extraVolumes and extraContainerVolumeMounts into the deployment dict

Both values are Deployment-scoped: `extraVolumes` is rendered into `spec.template.spec.volumes` and
`extraContainerVolumeMounts` only into the volumeMounts of the Gitea container. The `extra*` prefix said
nothing about that scope and left them sitting at the top level, far away from the pod- and container-scoped
settings that already live under `deployment` and `deployment.gitea`.

They therefore become `deployment.volumes` and `deployment.gitea.volumeMounts`, which makes the target
resource and container obvious from the values path alone and continues the consolidation started with
`deployment.gitea.env`, `deployment.gitea.image`, `deployment.gitea.resources` and the security contexts.

`extraInitVolumeMounts` stays where it is for now, because it targets the init containers rather than the
Gitea container. The deprecated `extraVolumeMounts` fallback is kept intact and now points at
`deployment.gitea.volumeMounts` in its documentation.

Both removed keys are covered by the deprecation check, because silently ignoring them would drop mounted
TLS certificates, custom themes or client certs and leave Gitea running with a broken or unexpected
configuration.

BREAKING CHANGE: `extraVolumes` and `extraContainerVolumeMounts` no longer exist. Use `deployment.volumes`
and `deployment.gitea.volumeMounts` 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

@@ -457,8 +457,8 @@ spec:
           secret:
             secretName: {{ include "gitea.secret.config.name" . }}
             defaultMode: 110
-        {{- if gt (len .Values.extraVolumes) 0 }}
-        {{- toYaml .Values.extraVolumes | nindent 8 }}
+        {{- if gt (len .Values.deployment.volumes) 0 }}
+        {{- toYaml .Values.deployment.volumes | nindent 8 }}
         {{- end }}
         - name: inline-config-sources
           secret: