(helm/v2-alpha): Fix cross-namespace RBAC file naming and templating

Fixes handling of namespace-scoped Roles and RoleBindings in cross-namespace
scenarios (e.g., for leader election, cross-namespace permissions).

Changes:
1. File naming: Append namespace suffix only when RBAC namespace differs from
   manager namespace to prevent file collisions
   - Manager namespace: leader-election-role.yaml (no suffix)
   - Cross-namespace: manager-role-infrastructure.yaml (suffix added)

2. Namespace templating: Manager namespace references replaced with
   {{ .Release.Namespace }}, cross-namespace metadata preserved as-is
   - Role in manager NS: namespace: {{ .Release.Namespace }}
   - Role in other NS: namespace: infrastructure (unchanged)
   - Subjects always: namespace: {{ .Release.Namespace }}

3. Manager namespace detection: Extract from Deployment resource instead of
   assuming <prefix>-system pattern

Result: Cross-namespace RBAC resources now generate correctly with explicit
namespaces preserved and unique filenames, while manager-namespace resources
are properly templated for Helm release flexibility."

Assisted-by: Cursor

Author: camilamacedo86