[rust-3p] Make async-io a fork

We want to add smol-rs/async-io#79 to our
distribution of async-io, so move it to forks.

Change-Id: Iccdab4f4a6aed7b773dbe200f07ce4e4f0bc9a05
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/871499
Reviewed-by: Steven Grady <slgrady@google.com>
Reviewed-by: Adam Perry <adamperry@google.com>
Fuchsia-Auto-Submit: Casey Dahlin <sadmac@google.com>
Commit-Queue: Casey Dahlin <sadmac@google.com>

Author: sadmac7000

third_party/rust_crates/BUILD.gn

@@ -1528,7 +1528,7 @@ rust_library("async-fs-v1_6_0") {
 
 rust_library("async-io-v1_12_0") {
   crate_name = "async_io"
-  crate_root = "//third_party/rust_crates/vendor/async-io-1.12.0/src/lib.rs"
+  crate_root = "//third_party/rust_crates/forks/async-io/src/lib.rs"
   output_name = "async_io-8cea39e881d5ae1e"
   configs -= [ "//build/config/rust:2018_idioms" ]
 

third_party/rust_crates/Cargo.lock

@@ -341,6 +341,7 @@ windows = { path = "empty/windows" }
 windows-sys = { path = "empty/windows-sys" }
 
 ### Forks: vendored crates whose code doesn't match the upstream version
+async-io = { path = "forks/async-io" }
 fatfs = { path = "forks/fatfs" }
 fuse3 = { path = "forks/fuse3" }
 hound = { path = "forks/hound" }