Migrate to cargo_embargo. am: 02ad4c1108

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

Change-Id: Ie912133b79ae86ee7aca2992a71e73214d33d65b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>