Replace CSRF cookie with CrossOriginProtection (#36183)

Removes the CSRF cookie in favor of
[`CrossOriginProtection`](https://pkg.go.dev/net/http#CrossOriginProtection)
which relies purely on HTTP headers.

Fixes: https://github.com/go-gitea/gitea/issues/11188
Fixes: https://github.com/go-gitea/gitea/issues/30333
Helps: https://github.com/go-gitea/gitea/issues/35107

TODOs:

- [x] Fix tests
- [ ] Ideally add tests to validates the protection

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/editor/fork.tmpl

@@ -4,7 +4,6 @@
 	<div class="ui container">
 		{{template "base/alert" .}}
 		<form class="ui form form-fetch-action" method="post" action="{{.RepoLink}}/_fork/{{.BranchName | PathEscapeSegments}}">
-			{{.CsrfTokenHtml}}
 			<div class="tw-text-center">
 				<div class="tw-my-[40px]">
 					<h3>{{ctx.Locale.Tr "repo.editor.fork_create"}}</h3>