Publish CsrfTokenRepository as a shared configurer bean

[jzheaux]

Related to #8731, configurers can benefit from knowing the CsrfTokenRepository that has been configured.

For example, this is helpful when Saml2LogoutConfigurer configures the CsrfLogoutHandler.

[jzheaux]

The original impetus for this ticket is #8731 and since it has been reopened for additional research, we'll reopen this one as well, just in case changes there require changes here.