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/applications_oauth2_list.tmpl

@@ -51,7 +51,6 @@
 	<details {{if .application_name}}open{{end}}>
 		<summary><h4 class="ui header tw-inline-block tw-my-2">{{ctx.Locale.Tr "settings.create_oauth2_application"}}</h4></summary>
 		<form class="ui form ignore-dirty" action="{{.Link}}/oauth2" method="post">
-			{{.CsrfTokenHtml}}
 			<div class="field {{if .Err_AppName}}error{{end}}">
 				<label for="application-name">{{ctx.Locale.Tr "settings.oauth2_application_name"}}</label>
 				<input id="application-name" name="application_name" value="{{.application_name}}" required maxlength="255">