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>

modules/setting/security.go

@@ -36,8 +36,6 @@ var (
 	PasswordCheckPwn                   bool
 	SuccessfulTokensCacheSize          int
 	DisableQueryAuthToken              bool
-	CSRFCookieName                     = "_csrf"
-	CSRFCookieHTTPOnly                 = true
 	RecordUserSignupMetadata           = false
 	TwoFactorAuthEnforced              = false
 )
@@ -139,7 +137,6 @@ func loadSecurityFrom(rootCfg ConfigProvider) {
 		log.Fatal("The provided password hash algorithm was invalid: %s", sec.Key("PASSWORD_HASH_ALGO").MustString(""))
 	}
 
-	CSRFCookieHTTPOnly = sec.Key("CSRF_COOKIE_HTTP_ONLY").MustBool(true)
 	PasswordCheckPwn = sec.Key("PASSWORD_CHECK_PWN").MustBool(false)
 	SuccessfulTokensCacheSize = sec.Key("SUCCESSFUL_TOKENS_CACHE_SIZE").MustInt(20)