Use test context in tests and new loop system in benchmarks (#33648)

Replace all contexts in tests with go1.24 t.Context()

---------

Co-authored-by: Giteabot <teabot@gitea.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/markup/markdown/markdown_benchmark_test.go

@@ -12,14 +12,14 @@ import (
 
 func BenchmarkSpecializedMarkdown(b *testing.B) {
 	// 240856	      4719 ns/op
-	for i := 0; i < b.N; i++ {
+	for b.Loop() {
 		markdown.SpecializedMarkdown(&markup.RenderContext{})
 	}
 }
 
 func BenchmarkMarkdownRender(b *testing.B) {
 	// 23202	     50840 ns/op
-	for i := 0; i < b.N; i++ {
+	for b.Loop() {
 		_, _ = markdown.RenderString(markup.NewTestRenderContext(), "https://example.com\n- a\n- b\n")
 	}
 }