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/user/settings/organization.tmpl

@@ -24,7 +24,6 @@
 						</div>
 						<div class="flex-item-trailing">
 							<form>
-								{{$.CsrfTokenHtml}}
 								<button class="ui red button delete-button" data-modal-id="leave-organization"
 												data-url="{{.OrganisationLink}}/members/action/leave" data-datauid="{{$.SignedUser.ID}}"
 												data-name="{{$.SignedUser.DisplayName}}"