Refactor htmx and fetch-action related code (#37186)

This is the first step (the hardest part):

* repo file list last commit message lazy load
* admin server status monitor
* watch/unwatch (normal page, watchers page)
* star/unstar (normal page, watchers page)
* project view, delete column
* workflow dispatch, switch the branch
* commit page: load branches and tags referencing this commit

The legacy "data-redirect" attribute is removed, it only makes the page
reload (sometimes using an incorrect link).

Also did cleanup for some devtest pages.

templates/repo/user_cards.tmpl

@@ -1,14 +1,5 @@
-<!-- Refresh the content if a htmx response contains "HX-Trigger" header.
-This usually happens when a user stays on the watchers/stargazers page
-when they watched/unwatched/starred/unstarred and the list should be refreshed.
-To test go to the watchers page and click the watch button. The user cards should reload.
-At the moment, no JS initialization would re-trigger (fortunately there is no JS for this page).
--->
-<div class="no-loading-indicator tw-hidden"></div>
-<div class="user-cards"
-		hx-trigger="refreshUserCards from:body" hx-indicator=".no-loading-indicator"
-		hx-get="" hx-swap="outerHTML" hx-select=".user-cards"
->
+{{/* need to reload after "watch/unwatch" or "star/unstar" fetch actions */}}
+<div class="user-cards" id="user-cards-container" data-fetch-trigger="fetch-reload">
 	{{if .CardsTitle}}
 	<h2 class="ui dividing header">
 		{{.CardsTitle}}