Refactor markup render to fix various path problems (#34114)

* Fix #33972
    * Use consistent path resolving for links and medias.
* No need to make the markup renders to resolve the paths, instead, the
paths are all correctly resolved in the "post process" step.
* Fix #33274
* Since 1.23, all paths starting with "/" are relative to current render
context (for example: the current repo branch)
* Introduce `/:root/path-relative-to-root`, then the path will be
rendered as relative to "ROOT_URL"

modules/markup/markdown/goldmark.go

@@ -65,10 +65,6 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 			g.transformHeading(ctx, v, reader, &tocList)
 		case *ast.Paragraph:
 			g.applyElementDir(v)
-		case *ast.Image:
-			g.transformImage(ctx, v)
-		case *ast.Link:
-			g.transformLink(ctx, v)
 		case *ast.List:
 			g.transformList(ctx, v, rc)
 		case *ast.Text: