refactor!: move openshift.hostUsers to deployment.hostUsers

The PodSpec `hostUsers` field has nothing to do with the OpenShift compatibility profile. It only selects whether the
pod shares the host's user namespace, which is a plain Kubernetes feature. Nesting it below `openshift` implied that it
requires OpenShift and, worse, the helper only rendered it when `openshift.enabled` evaluated to `true`, so the setting
was silently ignored on vanilla Kubernetes clusters.

`gitea.hostUsers` now reads `deployment.hostUsers` and no longer depends on the OpenShift profile. The value is only
rendered when it is an actual boolean, so the field stays omitted for `null` and the platform default applies.

BREAKING CHANGE: `openshift.hostUsers` has been removed. Configure `deployment.hostUsers` instead.

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

unittests/helm/deployment/deprecations.yaml

@@ -70,6 +70,12 @@ tests:
     asserts:
       - failedTemplate:
           errorMessage: "`nodeSelector` does no longer exist. Please refer to the changelog and configure `deployment.nodeSelector` instead."
+  - it: fails when the removed `openshift.hostUsers` value is set
+    set:
+      openshift.hostUsers: false
+    asserts:
+      - failedTemplate:
+          errorMessage: "`openshift.hostUsers` does no longer exist. Please refer to the changelog and configure `deployment.hostUsers` instead."
   - it: fails when the removed `priorityClassName` value is set
     set:
       priorityClassName: high-priority