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/admin/auth/edit.tmpl

@@ -6,7 +6,6 @@
 		<div class="ui attached segment">
 			<form class="ui form" action="{{.Link}}" method="post">
 				{{template "base/disable_form_autofill"}}
-				{{.CsrfTokenHtml}}
 				<input type="hidden" name="id" value="{{.Source.ID}}">
 				<div class="inline field">
 					<label>{{ctx.Locale.Tr "admin.auths.auth_type"}}</label>

templates/admin/auth/new.tmpl

@@ -6,7 +6,6 @@
 		<div class="ui attached segment">
 			<form class="ui form" action="{{.Link}}" method="post">
 				{{template "base/disable_form_autofill"}}
-				{{.CsrfTokenHtml}}
 				<!-- Types and name -->
 				<div class="inline required field {{if .Err_Type}}error{{end}}">
 					<label>{{ctx.Locale.Tr "admin.auths.auth_type"}}</label>