setDeviceToken

Registers or refreshes the FCM push pushToken with PingOne.

Should be called each time Firebase delivers a new token via FirebaseMessagingService.onNewToken, and immediately after initialize succeeds.

The native SDK may attempt to register the token across multiple PingOne regions. Returns Result.success when all registrations succeed (or the errors array contains only nulls — which the SDK uses to indicate no real errors). Returns Result.failure wrapping a PingOneMFAException if any region rejects the token; PingOneMFAException.internalErrorsList will contain one Error per failed region for diagnostic logging.