Migrate to cargo_embargo. am: 02ad4c1108 am: 60d782f8d6

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/cexpr/+/2822396

Change-Id: I9a88279364f8f48feb30cd929f44affa4c5970a0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>