Import async-stream-impl v0.3.0 am: 4d90486f87 am: c3955df4a0

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/async-stream-impl/+/1594011

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I5a8d3c9aa45933de8bdd2dbf98ce434715ed7d74