Update supplicant callbacks with reccomendations

from the ANAPIC review.

- Declare entire callback interfaces as oneway
  rather than each individual function.
- Remove onTerminating() method from ISupplicantCallback.

Bug: 215566635
Test: atest VtsHalWifiSupplicantStaIfaceTargetTest \
            VtsHalWifiSupplicantStaNetworkTargetTest \
            VtsHalWifiSupplicantP2pIfaceTargetTest
Change-Id: Ia9c95ef1ad7ada99a7f778ea063b9036cb4e3b42