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.

web_src/js/utils.ts

@@ -84,11 +84,6 @@ export function parseIssuePageInfo(): IssuePageInfo {
   };
 }
 
-/** parse a URL, either relative '/path' or absolute 'https://localhost/path' */
-export function parseUrl(str: string): URL {
-  return new URL(str, str.startsWith('http') ? undefined : window.location.origin);
-}
-
 /** return current locale chosen by user */
 export function getCurrentLocale(): string {
   return document.documentElement.lang;