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/org/settings/options.tmpl

@@ -6,7 +6,6 @@
 	</h4>
 	<div class="ui attached segment">
 		<form class="ui form" action="{{.Link}}" method="post">
-			{{.CsrfTokenHtml}}
 			<div class="field {{if .Err_FullName}}error{{end}}">
 				<label for="full_name">{{ctx.Locale.Tr "org.org_full_name_holder"}}</label>
 				<input id="full_name" name="full_name" value="{{.Org.FullName}}" maxlength="100">
@@ -57,7 +56,6 @@
 		<div class="divider"></div>
 
 		<form class="ui form" action="{{.Link}}/avatar" method="post" enctype="multipart/form-data">
-			{{.CsrfTokenHtml}}
 			<div class="inline field">
 				{{template "shared/avatar_upload_crop" dict "LabelText" (ctx.Locale.Tr "settings.choose_new_avatar")}}
 			</div>

templates/org/settings/options_dangerzone.tmpl

@@ -47,7 +47,6 @@
 			</ul>
 		</div>
 		<form class="ui form form-fetch-action" action="{{.Link}}/visibility" method="post">
-			{{.CsrfTokenHtml}}
 			<input type="hidden" name="current_visibility" value="{{.CurrentVisibility}}">
 			<div class="tw-flex tw-flex-col tw-gap-3">
 				<label>{{ctx.Locale.Tr "org.settings.visibility"}}</label>
@@ -85,7 +84,6 @@
 			</ul>
 		</div>
 		<form class="ui form form-fetch-action" action="{{.Link}}/rename" method="post">
-			{{.CsrfTokenHtml}}
 			<div class="field">
 				<label>
 					{{ctx.Locale.Tr "org.settings.name_confirm"}}
@@ -124,7 +122,6 @@
 			</ul>
 		</div>
 		<form class="ui form form-fetch-action" action="{{.Link}}/delete" method="post">
-			{{.CsrfTokenHtml}}
 			<div class="field">
 				<label>
 					{{ctx.Locale.Tr "org.settings.name_confirm"}}