v0.2.4

Refactoring and minor fixes/enhancements

• Use linear backoff with retry interval only for loading kubeconfig only if the referenced
  secret is not found; for other errors, enter regular controller-runtime error backoff.
• Helm generator: add forgotten filepath.Clean() invocations.
• Reconciler: add some locking to prevent out-of-order or problematic concurrent calls.
• Scaffold: bump versions.