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_inputs_test.go

@@ -62,9 +62,8 @@ jobs:
 		// run the workflow with os=windows
 		urlStr := fmt.Sprintf("/%s/%s/actions/run?workflow=%s", user2.Name, repo.Name, "test-inputs-context.yml")
 		req := NewRequestWithValues(t, "POST", urlStr, map[string]string{
-			"_csrf": GetUserCSRFToken(t, session),
-			"ref":   "refs/heads/main",
-			"os":    "windows",
+			"ref": "refs/heads/main",
+			"os":  "windows",
 		})
 		session.MakeRequest(t, req, http.StatusSeeOther)