Disable DTLS fingerprint verification

[UE2020]

It seems that it was possible to disable DTLS fingerprint verification at some point (at least v0.2.0), but now the fingerprint_verification config option doesn't go anywhere after Rtc::new_from_config is called. The old implementation wrapped output.push_back(DtlsEvent::RemoteFingerprint(fingerprint)); (here) in an if statement:

if self.fingerprint_verification {
    self.events
        .push_back(DtlsEvent::RemoteFingerprint(fingerprint));
}

Could this be added back?

[algesten]

Must have been a victim of the DTLS/crypto refactoring we did a while back. Let's add it back. PR welcome!