Migrate to cargo_embargo. am: b6eaca7d40 am: f17c297774 am: 01ed8f05ec

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/serde_spanned/+/2828071

Change-Id: If046cb20b7f43a165cfdd5fd13d6a4859d809b60
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>