Provisioning: Block Library Panel creation in provisioned folders (#114933)

* WIP: Block Library Panel creation in provisioned folders

* blocking patch - adding integration tests

* checking code in tests

* addressing comments, adding one more test

pkg/services/libraryelements/model/model.go

@@ -161,6 +161,8 @@ var (
 	ErrLibraryElementInvalidUID = errors.New("uid contains illegal characters")
 	// errLibraryElementUIDTooLong is an error for when the uid of a library element is invalid
 	ErrLibraryElementUIDTooLong = errors.New("uid too long, max 40 characters")
+	// ErrLibraryElementProvisionedFolder indicates that a library element cannot be created on a provisioned folder.
+	ErrLibraryElementProvisionedFolder = errors.New("resource type not supported in repository-managed folders")
 )
 
 // Commands