Migrate to cargo_embargo. am: 8725301739

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/shared_child/+/2838082

Change-Id: Iaeecd7ada20f88b2a05d84e955a18aede801b5ad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>