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/migrate/codebase.tmpl

@@ -8,7 +8,6 @@
 			{{template "base/alert" .}}
 			<form class="ui form left-right-form" action="{{.Link}}" method="post">
 				{{template "base/disable_form_autofill"}}
-				{{.CsrfTokenHtml}}
 
 				<input id="service_type" type="hidden" name="service" value="{{.service}}">