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>

routers/web/user/setting/keys.go

@@ -325,7 +325,7 @@ func loadKeysData(ctx *context.Context) {
 	ctx.Data["GPGKeys"] = gpgkeys
 	tokenToSign := asymkey_model.VerificationToken(ctx.Doer, 1)
 
-	// generate a new aes cipher using the csrfToken
+	// generate a new aes cipher using the token
 	ctx.Data["TokenToSign"] = tokenToSign
 
 	principals, err := db.Find[asymkey_model.PublicKey](ctx, asymkey_model.FindPublicKeyOptions{