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/web/web.go

@@ -1710,7 +1710,7 @@ func registerWebRoutes(m *web.Router, webAuth *AuthMiddleware) {
 
 		m.Get("/forks", repo.Forks)
 		m.Get("/commit/{sha:([a-f0-9]{7,64})}.{ext:patch|diff}", repo.MustBeNotEmpty, repo.RawDiff)
-		m.Post("/lastcommit/*", context.RepoRefByType(git.RefTypeCommit), repo.LastCommit)
+		m.Get("/lastcommit/*", context.RepoRefByType(git.RefTypeCommit), repo.LastCommit)
 	}, optSignIn, context.RepoAssignment, reqUnitCodeReader)
 	// end "/{username}/{reponame}": repo code