chore: clean up tests (#37715)

1. use MockVariableValue as much as possible
2. use wg.Go as much as possible instead of Add/Done
3. simplify global lock's DefaultLocker logic to make it easier to test
4. introduce a general approach for getting external service config in
CI
5. remove unclear & unnecessary "t.Skip"
6. use modern generic syntax for remaining "DecodeJSON" calls
7. clarify test result for "list gitignore templates" and "list
licenses"

tests/integration/api_pull_review_test.go

@@ -556,9 +556,7 @@ func testAPIPullReviewCommentReply(t *testing.T) {
 	// happy path
 	req := NewRequestWithJSON(t, http.MethodPost, url, &api.CreatePullReviewCommentReplyOptions{Body: "the reply"}).AddTokenAuth(token)
 	resp := MakeRequest(t, req, http.StatusCreated)
-
-	var reply api.PullReviewComment
-	DecodeJSON(t, resp, &reply)
+	reply := DecodeJSON(t, resp, &api.PullReviewComment{})
 	assert.Equal(t, "the reply", reply.Body)
 	assert.Equal(t, parent.ReviewID, reply.ReviewID)
 	assert.Equal(t, "README.md", reply.Path)