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/admin/dashboard.tmpl

@@ -10,7 +10,6 @@
 		</h4>
 		<div class="ui attached table segment">
 			<form method="post" action="{{AppSubUrl}}/-/admin">
-				{{.CsrfTokenHtml}}
 				<table class="ui very basic table tw-mt-0 tw-px-4">
 					<tbody>
 						<tr>