Improve Wiki TOC (#24137)

The old code has a lot of technical debts, eg: `repo/wiki/view.tmpl` /
`Iterate`

This PR improves the Wiki TOC display and improves the code.

---------

Co-authored-by: delvh <dev.lh@web.de>

routers/web/repo/wiki.go

@@ -298,7 +298,15 @@ func renderViewPage(ctx *context.Context) (*git.Repository, *git.TreeEntry) {
 		ctx.Data["footerPresent"] = false
 	}
 
-	ctx.Data["toc"] = rctx.TableOfContents
+	if rctx.SidebarTocNode != nil {
+		sb := &strings.Builder{}
+		err = markdown.SpecializedMarkdown().Renderer().Render(sb, nil, rctx.SidebarTocNode)
+		if err != nil {
+			log.Error("Failed to render wiki sidebar TOC: %v", err)
+		} else {
+			ctx.Data["sidebarTocContent"] = sb.String()
+		}
+	}
 
 	// get commit count - wiki revisions
 	commitsCount, _ := wikiRepo.FileCommitsCount(wiki_service.DefaultBranch, pageFilename)