Update BackupTransportCallback to use async AIDL

Bug: 202716271
Test: 1. Unit tests WIP
      2. atest CtsBackupTestCases CtsBackupHostTestCases
         GtsBackupTestCases GtsBackupHostTestCases
Change-Id: Ifa45f35a415ef3c5fbab03696456fd7085568a7b
3 files changed