test: consolidate Go tests (#39962)

Consolidate all Go tests. Coverage is identical to before. Go tests are
around 5% faster while being 7% smaller. No non-test code is touched.

models/renderhelper/simple_document_test.go

@@ -6,14 +6,12 @@ package renderhelper
 import (
 	"testing"
 
-	"gitea.dev/models/unittest"
 	"gitea.dev/modules/markup/markdown"
 
 	"github.com/stretchr/testify/assert"
 )
 
 func TestSimpleDocument(t *testing.T) {
-	unittest.PrepareTestEnv(t)
 	rctx := NewRenderContextSimpleDocument(t.Context(), "/base").WithMarkupType(markdown.MarkupName)
 	rendered, err := testRenderString(rctx, `
 65f1bf27bc3bf70f64657658635e66094edbcb4d