Implement supported values API in GRPC VHAL client/server.

Define new protobuf interface for GRPC VHAL. Implement the GRPC
VHAL client/server.

Test: Manual test on cf.
atest GRPCVehicleHardwareUnitTest GRPCVehicleProxyServerUnitTest
Flag: EXEMPT HAL
Bug: 393154530

Change-Id: I9252d6f42a5f43f1829f431887126142d69102f9