feat(deployment)!: move nodeSelector to deployment.nodeSelector

`nodeSelector` was a top-level value although it exclusively configures the pod spec of the Gitea Deployment.
With `affinity`, `dnsConfig` and the container environment already moved into the `deployment` dict, keeping
`nodeSelector` at the root level leaves the scheduling configuration split across two places.

Moving it into the `deployment` dict continues the consolidation of Deployment-scoped values and keeps
`nodeSelector` next to the closely related `affinity` setting. The `@param` annotations are grouped with the
values they document so the generated README table stays in sync with the structure.

A deprecation check is added so that existing installations fail fast with an actionable error message. Without
it, the node selection would be dropped silently and pods could be scheduled on nodes that do not meet the
intended requirements.

BREAKING CHANGE: `nodeSelector` no longer exists. Use `deployment.nodeSelector` instead. Installations that
still set `nodeSelector` will fail unless `checkDeprecation` is set to `false`.

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

unittests/helm/deployment/deprecations.yaml

@@ -39,6 +39,13 @@ tests:
     asserts:
       - failedTemplate:
           errorMessage: "`dnsConfig` does no longer exist. Please refer to the changelog and configure `deployment.dnsConfig` instead."
+  - it: fails when the removed `nodeSelector` value is set
+    set:
+      nodeSelector:
+        foo: bar
+    asserts:
+      - failedTemplate:
+          errorMessage: "`nodeSelector` does no longer exist. Please refer to the changelog and configure `deployment.nodeSelector` instead."
   - it: skips the deprecation checks when `checkDeprecation` is disabled
     set:
       checkDeprecation: false
@@ -50,6 +57,8 @@ tests:
       dnsConfig:
         nameservers:
           - 192.0.2.1
+      nodeSelector:
+        foo: bar
     asserts:
       - hasDocuments:
           count: 0