Add unique message id to an outgoing SMS

This is to ensure that the datagram dispatcher can distinguish between different messages.

Change-Id: I94af4367c1b369f79b07ec234548618e9cd54dad
FLAG: com.android.internal.telephony.flags.carrier_roaming_nb_iot_ntn 
Bug: 369502538
Test: atest GsmSmsDispatcherTest ImsSmsDispatcherTest CdmaSmsDispatcherTest SmsDispatchersControllerTest
Manually test send P2P SMS over NTN using test app https://buganizer.corp.google.com/issues/369502538#comment5
Manual sanity test: b/371081001