webauthn: use DefaultResourcesFilter without reflection

[Kehrlann]

reviewer: @rwinch

Description

Use DefaultResourcesFilter with a proper static method for webauthn pages.

Note that the filter used to be registered only when the DefaultLoginPageGeneratingFilter was registered. It is now always used, because the DefaultWebAuthnRegistrationPageGeneratingFilter uses the javascript, and that file is always present. Also note that while the registration page is after the AuthorizationFilter, the javascript will always be publicly served, because, when the login page is served, it needs the javascript to be publicly accessible.