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/system_status.tmpl

@@ -1,4 +1,4 @@
-<dl class="admin-dl-horizontal">
+<dl class="admin-dl-horizontal" data-fetch-url="{{AppSubUrl}}/-/admin/system_status" data-fetch-sync="$morph" data-fetch-trigger="every 5s">
 	<dt>{{ctx.Locale.Tr "admin.dashboard.server_uptime"}}</dt>
 	<dd><relative-time format="duration" datetime="{{.SysStatus.StartTime}}">{{.SysStatus.StartTime}}</relative-time></dd>
 	<dt>{{ctx.Locale.Tr "admin.dashboard.current_goroutine"}}</dt>