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>

services/context/context_cookie.go

@@ -25,13 +25,11 @@ func removeSessionCookieHeader(w http.ResponseWriter) {
 }
 
 // SetSiteCookie convenience function to set most cookies consistently
-// CSRF and a few others are the exception here
 func (ctx *Context) SetSiteCookie(name, value string, maxAge int) {
 	middleware.SetSiteCookie(ctx.Resp, name, value, maxAge)
 }
 
 // DeleteSiteCookie convenience function to delete most cookies consistently
-// CSRF and a few others are the exception here
 func (ctx *Context) DeleteSiteCookie(name string) {
 	middleware.SetSiteCookie(ctx.Resp, name, "", -1)
 }