Create EmuMetadataGenerator to check meta.json.

Create EmuMetadataGenerator to convert AIDL generated java files
to meta.json that can be used by emulator to populate the available
vhal props list.

Added build rules to generate the Java files from AIDL files and
check whether the meta.json file needs to be updated.

Test: make sdk_car_x86_64-trunk_staging-userdebug target
Bug: 318747444
Change-Id: Ib3bc7b68a1312152617fdab4598ed389447c20cd
Merged-In: Ib3bc7b68a1312152617fdab4598ed389447c20cd