Migrate to cargo_embargo. am: 8db550a9e9 am: 5c4eeb65ff

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/threadpool/+/2828054

Change-Id: I5fb3f0afc89fad194c0012aa4075fd72da35b76f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>