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/collaboration.tmpl

@@ -40,7 +40,6 @@
 		{{end}}
 		<div class="ui bottom attached segment">
 			<form class="ui form" id="repo-collab-form" action="{{.Link}}" method="post">
-				{{.CsrfTokenHtml}}
 				<div id="search-user-box" class="ui search input tw-align-middle">
 					<input class="prompt" name="collaborator" placeholder="{{ctx.Locale.Tr "search.user_kind"}}" autocomplete="off" autofocus required>
 				</div>
@@ -108,7 +107,6 @@
 			<div class="ui bottom attached segment">
 				{{if $allowedToChangeTeams}}
 					<form class="ui form" id="repo-collab-team-form" action="{{.Link}}/team" method="post">
-						{{.CsrfTokenHtml}}
 						<div id="search-team-box" class="ui search input tw-align-middle" data-org-name="{{.OrgName}}">
 							<input class="prompt" name="team" placeholder="{{ctx.Locale.Tr "search.team_kind"}}" autocomplete="off" required>
 						</div>