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>

tests/integration/actions_approve_test.go

@@ -127,10 +127,7 @@ jobs:
 		)
 
 		// user2 approves all runs
-		req = NewRequestWithValues(t, "POST", dataURL,
-			map[string]string{
-				"_csrf": GetUserCSRFToken(t, user2Session),
-			})
+		req = NewRequest(t, "POST", dataURL)
 		user2Session.MakeRequest(t, req, http.StatusOK)
 
 		// check runs