Start cleaning the messy ".ui.left / .ui.right", improve label list page, fix stackable menu (#24393)

Since 2015/2016, there is a global pollution: ".ui.left" / ".ui.right".

Fomantic UI doesn't work this way, it just conflicts with many Fomantic
definitions.

This PR starts the cleaning work of such techinical debts.

And, the "label list" page has been quite messy for long time, for
example, why "li" appears in "div" ......

And fix #24296

<details>


![image](https://user-images.githubusercontent.com/2114189/235051281-54c5374c-b5fd-4b5f-9aa2-02d4bb2d9112.png)


![image](https://user-images.githubusercontent.com/2114189/235055703-2ba042e0-4db7-4e63-8646-02f390d496b5.png)


![image](https://user-images.githubusercontent.com/2114189/235056310-4f6ffdc2-5758-4927-8fb8-314d9fb72a6b.png)


![image](https://user-images.githubusercontent.com/2114189/235058400-dab1c9ec-3325-4671-8345-aee6b0b68042.png)


![image](https://user-images.githubusercontent.com/2114189/235058424-85509532-b9bc-43ad-b00f-a87184c60f22.png)

</details>

templates/repo/issue/list.tmpl

@@ -34,7 +34,7 @@
 				{{template "repo/issue/openclose" .}}
 			</div>
 			<div class="ten wide right aligned column">
-				<div class="ui secondary filter stackable menu labels">
+				<div class="ui secondary filter menu labels gt-overflow-x-auto gt-overflow-y-hidden">
 					<!-- Label -->
 					<div class="ui {{if not .Labels}}disabled{{end}} dropdown jump item label-filter" style="margin-left: auto">
 						<span class="text">