Migrate to cargo_embargo. am: 02ad4c1108 am: f56787c588 am: 4752388e99

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

Change-Id: I65ae38f028d9c39b1a5a000be28ad195242e2aad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>