Add Automotive OS API 29 stubs to platform SDK optionals. am: ecf644f2d6 am: 7737e3dc01 am: 683c5ffe37 am: 6edb7d4bfa

Original change: https://googleplex-android-review.googlesource.com/c/platform/development/+/12221485

Change-Id: Ic3213bbc3b53ce1fa863de6e4b6eb42925baeedb