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/emails/list.tmpl

@@ -83,8 +83,6 @@
 			<form class="content ui form" action="{{AppSubUrl}}/-/admin/emails/activate" method="post">
 				<p class="center">{{ctx.Locale.Tr "admin.emails.change_email_text"}}</p>
 
-				{{$.CsrfTokenHtml}}
-
 				<input type="hidden" name="sort" value="{{.SortType}}">
 				<input type="hidden" name="q" value="{{.Keyword}}">
 				<input type="hidden" name="is_primary" value="{{.IsPrimary}}">