Migrate to cargo_embargo. am: e2a9f1d164 am: 4b698ff1e5 am: b50d3639c3

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/rand_chacha/+/2822009

Change-Id: I1e2f2de340beacbebfb939fbeeca8b7042892f29
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>