Implement filter checks: ensure all defined filters are used and remove dead code

Integration tests added/updated:
- tests/integration/test_filters_usage.py: AST-based detection of filter definitions (FilterModule.filters), robust Jinja detection ({{ ... }}, {% ... %}, {% filter ... %}), plus Python call tracking; fails if a filter is used only under tests/.
- tests/integration/test_filters_are_defined.py: inverse check — every filter used in .yml/.yaml/.j2/.jinja2/.tmpl must be defined locally. Scans only inside Jinja blocks and ignores pipes inside strings (e.g., lookup('pipe', "... | grep ... | awk ...")) to avoid false positives like trusted_hosts, woff/woff2, etc.

Bug fixes & robustness:
- Build regexes without %-string formatting to avoid ValueError from literal '%' in Jinja tags.
- Strip quoted strings in usage analysis so sed/grep/awk pipes are not miscounted as filters.
- Prevent self-matches in the defining file.

Cleanup / removal of dead code:
- Removed unused filter plugins and related unit tests:
  * filter_plugins/alias_domains_map.py
  * filter_plugins/get_application_id.py
  * filter_plugins/load_configuration.py
  * filter_plugins/safe.py
  * filter_plugins/safe_join.py
  * roles/svc-db-openldap/filter_plugins/build_ldap_nested_group_entries.py
  * roles/sys-ctl-bkp-docker-2-loc/filter_plugins/dict_to_cli_args.py
  * corresponding tests under tests/unit/*
- roles/svc-db-postgres/filter_plugins/split_postgres_connections.py: dropped no-longer-needed list_postgres_roles API; adjusted tests.

Misc:
- sys-stk-front-proxy/defaults/main.yml: clarified valid vhost_flavour values (comma-separated).

Ref: https://chatgpt.com/share/68b56bac-c4f8-800f-aeef-6708dbb44199

roles/svc-db-postgres/filter_plugins/split_postgres_connections.py

@@ -37,22 +37,8 @@ def split_postgres_connections(total_connections, roles_dir="roles"):
     denom = max(count, 1)
     return max(1, total // denom)
 
-def list_postgres_roles(roles_dir="roles"):
-    """
-    Helper: return a list of role names that declare database_type: postgres in vars/main.yml.
-    """
-    names = []
-    if not os.path.isdir(roles_dir):
-        return names
-    for name in os.listdir(roles_dir):
-        vars_main = os.path.join(roles_dir, name, "vars", "main.yml")
-        if os.path.isfile(vars_main) and _is_postgres_role(vars_main):
-            names.append(name)
-    return names
-
 class FilterModule(object):
     def filters(self):
         return {
-            "split_postgres_connections": split_postgres_connections,
-            "list_postgres_roles": list_postgres_roles,
+            "split_postgres_connections": split_postgres_connections
         }