Migrate to cargo_embargo. am: 6fd24aae90

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/either/+/2796179

Change-Id: Ib538e624b2414037409046e9a64d5f17886d423d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>