Refactor markdown render (#32728)

Follow up recent render system refactoring PRs (split test code), and
fine tune the math render (added some new cases)

modules/markup/markdown/markdown_benchmark_test.go

@@ -0,0 +1,25 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown_test
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/markup"
+	"code.gitea.io/gitea/modules/markup/markdown"
+)
+
+func BenchmarkSpecializedMarkdown(b *testing.B) {
+	// 240856	      4719 ns/op
+	for i := 0; i < b.N; i++ {
+		markdown.SpecializedMarkdown(&markup.RenderContext{})
+	}
+}
+
+func BenchmarkMarkdownRender(b *testing.B) {
+	// 23202	     50840 ns/op
+	for i := 0; i < b.N; i++ {
+		_, _ = markdown.RenderString(markup.NewTestRenderContext(), "https://example.com\n- a\n- b\n")
+	}
+}