Generate apex_available from c2a instead of a patch am: 6a34237310 am: cda0442d52 am: a87de93277 am: dc7869c0e6

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-sink/+/1688689

Change-Id: I12898a3c17858a758b3f585c18e46db3efcc194e