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_issue_subscription_test.go

@@ -39,8 +39,7 @@ func TestAPIIssueSubscriptions(t *testing.T) {
 		req := NewRequest(t, "GET", fmt.Sprintf("/api/v1/repos/%s/%s/issues/%d/subscriptions/check", issueRepo.OwnerName, issueRepo.Name, issue.Index)).
 			AddTokenAuth(token)
 		resp := MakeRequest(t, req, http.StatusOK)
-		wi := new(api.WatchInfo)
-		DecodeJSON(t, resp, wi)
+		wi := DecodeJSON(t, resp, &api.WatchInfo{})
 
 		assert.Equal(t, isWatching, wi.Subscribed)
 		assert.Equal(t, !isWatching, wi.Ignored)