Migrate to cargo_embargo. am: d19ea6527f am: 1768b48aad am: e0ad8793ea

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-channel/+/2833071

Change-Id: I9444c5b81f9df301c3986a93d7599a26bd853f37
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>