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/create_no_session_test.go

@@ -12,6 +12,7 @@ import (
 
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
 	"code.gitea.io/gitea/routers"
 	"code.gitea.io/gitea/tests"
 
@@ -52,16 +53,11 @@ func sessionFileExist(t *testing.T, tmpDir, sessionID string) bool {
 
 func TestSessionFileCreation(t *testing.T) {
 	defer tests.PrepareTestEnv(t)()
-
-	oldSessionConfig := setting.SessionConfig.ProviderConfig
-	defer func() {
-		setting.SessionConfig.ProviderConfig = oldSessionConfig
-		testWebRoutes = routers.NormalRoutes()
-	}()
+	defer test.MockVariableValue(&setting.SessionConfig.ProviderConfig)()
+	defer test.MockVariableValue(&testWebRoutes)()
 
 	var config session.Options
-
-	err := json.Unmarshal([]byte(oldSessionConfig), &config)
+	err := json.Unmarshal([]byte(setting.SessionConfig.ProviderConfig), &config)
 	assert.NoError(t, err)
 
 	config.Provider = "file"