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/issue/labels/label_load_template.tmpl

@@ -2,7 +2,6 @@
 	<div class="twelve wide computer column">
 		<p>{{ctx.Locale.Tr "repo.issues.label_templates.info"}}</p>
 		<form class="ui form center" action="{{.Link}}/initialize" method="post">
-			{{.CsrfTokenHtml}}
 			<div class="field">
 				<div class="ui selection dropdown">
 					<input type="hidden" name="template_name" value="Default">