Add rust_test and update TEST_MAPPING am: ad0828c132 am: af0f896ebf am: c70b8ab742 am: ae53a6235c

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

Change-Id: I7c5bb226baeabc251b1527eb7455cc3e373a1142