Migrate to cargo_embargo. am: c15bd3ae8d am: 7cbd7caa94 am: 3ab49b09db

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/protobuf-json-mapping/+/2822213

Change-Id: I9e77db05b00af5b94b80139233d449f2cf3912bc
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>