QueryCaching: Use CachingServiceClient for query caching (#112128)

* Integrate mt querier with query caching

* typo

* let the caller set cache status response header

* fix TestQueryAPI

* make gen-go

* handle CachingServiceClient being nil and make gen-go

* include namespace in cache key

* set signed in user namespace in query_test.go

* fix test

* remove commented out code

* undo services/query/query.go changes

* make gen-go

* remove namespace requirement

* fix tests

* fix test

* remove namespace from SignedInUser in tests

* make gen-go

pkg/registry/apis/query/query_test.go

@@ -54,6 +54,10 @@ func (mu mockUser) GetOrgID() int64 {
 	return -1
 }
 
+func (mu mockUser) GetNamespace() string {
+	return "ns"
+}
+
 func TestQueryAPI(t *testing.T) {
 	testCases := []struct {
 		name           string