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/status/500.tmpl

@@ -31,7 +31,6 @@
 		<div class="divider tw-my-0"></div>
 		<div role="main" class="page-content status-page-500">
 			<div class="ui container" >
-				<style> .ui.message.flash-message { text-align: left; } </style>
 				{{template "base/alert" .}}
 				<div class="status-page-error">
 					<div class="status-page-error-title">500 Internal Server Error</div>