Migrate to cargo_embargo. am: eef4796c18 am: efb2acf134 am: 416fa00db4

Original change: https://android-review.googlesource.com/c/platform/external/rust/cxx/+/2882808

Change-Id: I2d903b8b829fe99b6894b2eb53533b166c720edf
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>