Refactor markup render system (#32612)

This PR removes (almost) all path tricks, and introduces "renderhelper"
package.

Now we can clearly see the rendering behaviors for comment/file/wiki,
more details are in "renderhelper" tests.

Fix #31411 , fix #18592, fix #25632 and maybe more problems. (ps: fix
#32608 by the way)

modules/markup/html_codepreview.go

@@ -51,7 +51,7 @@ func renderCodeBlock(ctx *RenderContext, node *html.Node) (urlPosStart, urlPosSt
 	lineStart, _ := strconv.Atoi(strings.TrimPrefix(lineStartStr, "L"))
 	lineStop, _ := strconv.Atoi(strings.TrimPrefix(lineStopStr, "L"))
 	opts.LineStart, opts.LineStop = lineStart, lineStop
-	h, err := DefaultProcessorHelper.RenderRepoFileCodePreview(ctx, opts)
+	h, err := DefaultRenderHelperFuncs.RenderRepoFileCodePreview(ctx, opts)
 	return m[0], m[1], h, err
 }