Refactor Policy Enforcer Configuration

- Updated the Policy Enforcer configuration across multiple YAML files to use a unified `policyDir` instead of individual policy sources.
- Changed the step name from `enforcePolicy` to `policyEnforcer` for consistency.
- Enhanced the documentation to clarify the use of `policyUrls`, `policyDir`, and `policyFile` for policy sources.
- Adjusted related code and tests to accommodate the new configuration structure.
- Added documentation for using YAML folded scalar (>-) to keep long comma-separated policyUrls values readable across multiple lines.

core/module/handler/stdHandler.go

@@ -354,7 +354,7 @@ func (h *stdHandler) initSteps(ctx context.Context, mgr PluginManager, cfg *Conf
 			s, err = newValidateSchemaStep(h.schemaValidator)
 		case "addRoute":
 			s, err = newAddRouteStep(h.router)
-		case "enforcePolicy":
+		case "policyEnforcer":
 			s, err = newEnforcePolicyStep(h.policyEnforcer)
 		default:
 			if customStep, exists := steps[step]; exists {