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

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

Change-Id: I008f079e817b8a2419c2ab2d77db5a2f0c40a5f6