Add metadata files for cast. am: 0fa02c0ba5 am: 75bab1892e am: 07b9d611a2 am: 5c15f84cf0

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/cast/+/1620971

Change-Id: I9eed159d4f9b01bb8351c75f75319e9686f26934