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/repo_watch_test.go

@@ -10,12 +10,13 @@ import (
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unittest"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
 )
 
 func TestRepoWatch(t *testing.T) {
 	onGiteaRun(t, func(t *testing.T, giteaURL *url.URL) {
 		// Test round-trip auto-watch
-		setting.Service.AutoWatchOnChanges = true
+		defer test.MockVariableValue(&setting.Service.AutoWatchOnChanges, true)()
 		session := loginUser(t, "user2")
 		unittest.AssertNotExistsBean(t, &repo_model.Watch{UserID: 2, RepoID: 3})
 		testEditFile(t, session, "org3", "repo3", "master", "README.md", "Hello, World (Edited for watch)\n")