Implement VMS HAL "Start Session" handshake.

Bug: 130313799
Test: Updated VmsHalServiceTest and VmsClientManagerTest
Test: Updated MockedVmsTestBase to include handshake
Test: atest AndroidCarApiTest CarServiceTest CarServiceUnitTest
Change-Id: I8d37362edb44152a29cf8a6b558529decd9bf6e9
6 files changed