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.

services/context/base.go

@@ -159,12 +159,10 @@ func (b *Base) Redirect(location string, status ...int) {
 		// So in this case, we should remove the session cookie from the response header
 		removeSessionCookieHeader(b.Resp)
 	}
-	// in case the request is made by htmx, have it redirect the browser instead of trying to follow the redirect inside htmx
-	if b.Req.Header.Get("HX-Request") == "true" {
-		b.Resp.Header().Set("HX-Redirect", location)
-		// we have to return a non-redirect status code so XMLHTTPRequest will not immediately follow the redirect
-		// so as to give htmx redirect logic a chance to run
-		b.Status(http.StatusNoContent)
+	// In case the request is made by "fetch-action" module, make JS redirect to the new location
+	// Otherwise, the JS fetch will follow the redirection and read a "login" page, embed it to the current page, which is not expected.
+	if b.Req.Header.Get("X-Gitea-Fetch-Action") != "" {
+		b.JSON(http.StatusOK, map[string]any{"redirect": location})
 		return
 	}
 	http.Redirect(b.Resp, b.Req, location, code)