test: align the file names of the helm unit tests with the chart conventions

The chart conventions demand camelCase file names, forbid short names like `svc` and require the unit tests to
mirror the template structure. The unit tests followed none of that consistently. Four casings existed side by
side - camelCase (extraInitContainers.yaml), kebab-case (checksum-annotations.yaml), a snake and kebab mix
(init_directory_structure.sh-rootless.yaml) and all caps (HA.yaml) - so there was no pattern to copy when
adding a suite, which is how the inconsistency kept growing.

Three groups of problems are fixed:

- svc-configuration.yaml used exactly the short name the conventions forbid for files and keys.
- Several file names repeated their own directory, for example deployment/deployment-additional-config.yaml and
  metric-secret/metrics-secret-servicemonitor-disabled.yaml, which names the subject three times. The directory
  already carries that information, so the file name now only carries the scenario. The default scenario of a
  template is named basics.yaml.
- Four suites lived in a directory of a template they do not assert on. They were filed under deployment/
  because the deployment is rendered as a side effect, not because it is the subject:

      deployment/deprecations.yaml                -> deprecation/deployment.yaml
      deployment/inline-config.yaml               -> config/inlineConfig.yaml
      deployment/storage-class-configuration.yaml -> persistentVolumeClaim/storageClass.yaml
      deployment/svc-configuration.yaml           -> service/configuration.yaml

  storage-class-configuration.yaml is the clearest case: a persistentVolumeClaim directory already existed next
  to it. The suite titles of the two suites whose subject changed are adjusted accordingly.

The Makefile passed `--file unittests/helm/values-conflicting-checks.yaml`, but that file does not exist in the
tree. `helm unittest` ignores a missing path without a warning, so the flag has been dead for an unknown amount
of time while still suggesting the checks run. It is removed; the `unittests/helm/**/*.yaml` glob would pick
the file up anyway if it ever returns.

The naming rule is written down in the copilot instructions, together with the constraint that the glob matches
only a single directory level, so a suite can never be placed directly in unittests/helm/.

All 49 suites and 267 tests still pass.

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

unittests/helm/persistentVolumeClaim/storageClass.yaml

@@ -0,0 +1,17 @@
+chart:
+  appVersion: 1.27.3
+release:
+  name: gitea-unittests
+  namespace: testing
+suite: Test persistentVolumeClaim storage class
+templates:
+  - templates/persistentVolumeClaim.yaml
+tests:
+  - it: "Render the storageClassName when persistence.new.storageClassName is defined"
+    set:
+      persistence.enabled: true
+      persistence.new.storageClassName: my-storage-class
+    asserts:
+      - equal:
+          path: spec.storageClassName
+          value: my-storage-class