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/user/settings/security/twofa_enroll.tmpl

@@ -9,7 +9,6 @@
 			<p>{{ctx.Locale.Tr "settings.or_enter_secret" .TwofaSecret}}</p>
 			<p>{{ctx.Locale.Tr "settings.then_enter_passcode"}}</p>
 			<form class="ui form" action="{{.Link}}" method="post">
-				{{.CsrfTokenHtml}}
 				<div class="inline required field {{if .Err_Passcode}}error{{end}}">
 					<label for="passcode">{{ctx.Locale.Tr "passcode"}}</label>
 					<input id="passcode" name="passcode" autofocus required>