Migrate to cargo_embargo. am: d939d4fef1 am: bd7eb5a76c

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/rand_core/+/2824510

Change-Id: I7ac39dba61365099b9bc3963e05a3143bbe77439
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>