Add rust_test and update TEST_MAPPING am: efbe0ef315 am: bbeeae3c36 am: c266fd138a am: ad9766c19d

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-sink/+/1366005

Change-Id: I44b212b62f6f1d093403081edf604f18497c5f68