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>

web_src/js/vitest.setup.ts

@@ -7,7 +7,6 @@ window.config = {
   assetUrlPrefix: '',
   runModeIsProd: true,
   customEmojis: {},
-  csrfToken: 'test-csrf-token-123456',
   pageData: {},
   notificationSettings: {},
   enableTimeTracking: true,