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/header.tmpl

@@ -41,7 +41,6 @@
 				<div class="flex-text-block tw-flex-wrap">
 					{{if $.RepoTransfer}}
 						<form method="post" action="{{$.RepoLink}}/action/accept_transfer?redirect_to={{$.RepoLink}}">
-							{{$.CsrfTokenHtml}}
 							<div class="flex-text-inline" data-tooltip-content="{{if $.CanUserAcceptOrRejectTransfer}}{{ctx.Locale.Tr "repo.transfer.accept_desc" $.RepoTransfer.Recipient.DisplayName}}{{else}}{{ctx.Locale.Tr "repo.transfer.no_permission_to_accept"}}{{end}}">
 								<button type="submit" class="ui compact small basic button {{if $.CanUserAcceptOrRejectTransfer}}primary {{end}} ok small"{{if not $.CanUserAcceptOrRejectTransfer}} disabled{{end}}>
 									{{ctx.Locale.Tr "repo.transfer.accept"}}
@@ -49,7 +48,6 @@
 							</div>
 						</form>
 						<form method="post" action="{{$.RepoLink}}/action/reject_transfer?redirect_to={{$.RepoLink}}">
-							{{$.CsrfTokenHtml}}
 							<div class="flex-text-inline" data-tooltip-content="{{if $.CanUserAcceptOrRejectTransfer}}{{ctx.Locale.Tr "repo.transfer.reject_desc" $.RepoTransfer.Recipient.DisplayName}}{{else}}{{ctx.Locale.Tr "repo.transfer.no_permission_to_reject"}}{{end}}">
 								<button type="submit" class="ui compact small basic button {{if $.CanUserAcceptOrRejectTransfer}}red {{end}}ok small"{{if not $.CanUserAcceptOrRejectTransfer}} disabled{{end}}>
 									{{ctx.Locale.Tr "repo.transfer.reject"}}