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/goget_test.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
 	"code.gitea.io/gitea/tests"
 
 	"github.com/stretchr/testify/assert"
@@ -36,12 +37,7 @@ func TestGoGet(t *testing.T) {
 
 func TestGoGetForSSH(t *testing.T) {
 	defer tests.PrepareTestEnv(t)()
-
-	old := setting.Repository.GoGetCloneURLProtocol
-	defer func() {
-		setting.Repository.GoGetCloneURLProtocol = old
-	}()
-	setting.Repository.GoGetCloneURLProtocol = "ssh"
+	defer test.MockVariableValue(&setting.Repository.GoGetCloneURLProtocol, "ssh")()
 
 	req := NewRequest(t, "GET", "/blah/glah/plah?go-get=1")
 	resp := MakeRequest(t, req, http.StatusOK)