Add support for async/streams/futures to Rust generator #2556

Job	Run time
Check	2m 11s
Test (ubuntu-latest, c)	5m 2s
Test (ubuntu-latest, rust)	4m 56s
Crate Unit Tests	1m 10s
Build wit-bindgen (x86_64-linux, ubuntu-latest)	1m 40s
Test (ubuntu-latest, teavm-java)	5m 4s
Build wit-bindgen (x86_64-macos, macos-latest, x86_64-apple-darwin)	1m 32s
Rustfmt	9s
Build wit-bindgen (aarch64-macos, macos-latest, aarch64-apple-darwin)	1m 38s
Test (ubuntu-latest, go)	5m 35s
verify-publish	28s
Build wit-bindgen (x86_64-windows, windows-latest)	3m 17s
Test (ubuntu-latest, csharp)	7m 56s
Build wit-bindgen (aarch64-linux, ubuntu-latest, aarch64-unknown-linux-gnu)	1m 47s
Test (macos-latest, c)	6m 13s
Test (macos-latest, rust)	7m 30s
Test (macos-latest, teavm-java)	4m 31s
Test (macos-latest, go)	8m 58s
Test (macos-latest, csharp)	11m 2s
Test (windows-latest, c)	9m 11s
Test (windows-latest, rust)	9m 2s
Test (windows-latest, teavm-java)	9m 32s
Test (windows-latest, go)	10m 25s
Test (windows-latest, csharp)	31m 1s
Record the result of testing and building steps	1s
	2h 29m 51s

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