Add metadata files for crossbeam-channel. am: c079bad89c am: b4f2d915f2 am: f0a63361ff am: 0cbe779429

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/crossbeam-channel/+/1620978

Change-Id: I38a53a2935f9d439b259265eec5bca5ad9e7fa35