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/admin/dashboard.tmpl

@@ -76,10 +76,7 @@
 		</h4>
 		{{/* TODO: make these stats work in multi-server deployments, likely needs per-server stats in DB */}}
 		<div class="ui attached table segment">
-			<div class="no-loading-indicator tw-hidden"></div>
-			<div hx-get="{{$.Link}}/system_status" hx-swap="morph:innerHTML" hx-trigger="every 5s" hx-indicator=".no-loading-indicator">
-				{{template "admin/system_status" .}}
-			</div>
+			{{template "admin/system_status" .}}
 		</div>
 	</div>
 {{template "admin/layout_footer" .}}