Migrate to cargo_embargo. am: d939d4fef1 am: 7010d0dfda

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

Change-Id: I8dca948f94b6534bbedac474ae95ed7f68f89d21
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>