Add rust_test and update TEST_MAPPING am: 1807259c44 am: 7a08a1d289 am: 5d70723ca9

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-task/+/1365231

Change-Id: I2a2544dc9ea48f401c20e757b17981dff46a6110