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/settings/lfs_pointers.tmpl

@@ -5,7 +5,6 @@
 			{{if gt .NumAssociatable 0}}
 				<div class="ui right">
 					<form class="ui form" method="post" action="{{$.Link}}/associate">
-						{{.CsrfTokenHtml}}
 						{{range .Pointers}}
 							{{if .Associatable}}
 								<input type="hidden" name="oid" value="{{.Oid}} {{.Size}}">