Add rust_test and update TEST_MAPPING am: 35dedf6a77 am: ff20eba123 am: e6fcd6b3bb am: 847dd5114f am: 4612338428

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/protobuf-codegen/+/1365084

Change-Id: Ie1ad63bc41b2bf23cef114c0d5d2b7e612e5f37d