Migrate to cargo_embargo. am: 81325be9a8 am: 52667474f5 am: e57a6e97d0

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/unicode-ident/+/2828192

Change-Id: I05dda060d88275fa857af35913bb7c5a154fea27
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>