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.

routers/common/redirect.go

@@ -16,8 +16,8 @@ func FetchRedirectDelegate(resp http.ResponseWriter, req *http.Request) {
 	// 2. when use "window.reload()", the hash is not respected, the newly loaded page won't scroll to the hash target.
 	// The typical page is "issue comment" page. The backend responds "/owner/repo/issues/1#comment-2",
 	// then frontend needs this delegate to redirect to the new location with hash correctly.
-	redirect := req.PostFormValue("redirect")
-	if !httplib.IsCurrentGiteaSiteURL(req.Context(), redirect) {
+	redirect := req.FormValue("redirect")
+	if req.Method != http.MethodPost || !httplib.IsCurrentGiteaSiteURL(req.Context(), redirect) {
 		resp.WriteHeader(http.StatusBadRequest)
 		return
 	}