Add rust_test and update TEST_MAPPING am: ad0828c132 am: af0f896ebf am: c70b8ab742

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/proc-macro-nested/+/1366082

Change-Id: I56692c32f86415cfdd78b0112b44e51b1369591c