Add rust_test and update TEST_MAPPING am: 21b311173f am: 099778819d am: fb2a890f29 am: 562da7adf7 am: 136646bceb

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/bitflags/+/1365661

Change-Id: I3dc52675c602cdf87089516b26f94d357be3bb94