Convert sdk_car_* from 32/64-bit-mixed to 64-bit-only build

Drop legacy 32-bit app support for sdk_car_arm64, sdk_car_x86_64,
and sdk_car_md_x86_64.mk to align with Google car emulators
(sdk_gcar_* and gcar_emu_*).

Bug: 262800138
Test: build and launch sdk_car_x86_64 emulator
Change-Id: Ib5119cd98138e6f840c7a591dd049c7f72f69f14
4 files changed