Registration omitted `userVerification`, so Chromium raised the
credential to credProtect level 3 and the authenticator then hid it from
the second-factor login, which asked for `discouraged`. Registration and
each login now set their own value, with `preferred` on the second
factor so credentials already registered at level 3 keep working without
re-enrollment.
Also add relevant e2e test coverage for webauthn, one test chromium only
because Firefox lacks the APIs needed.
Fixes https://github.com/go-gitea/gitea/issues/33531
Fixes https://github.com/go-gitea/gitea/issues/36019
Fixes https://github.com/go-gitea/gitea/issues/38139
silverwind