windows: drop dependency on windows-sys #227

Job	Run time
cross-ios-build (nightly, aarch64-apple-ios)	19s
windows-test (nightly, x86_64-pc-windows-gnu)	1m 0s
cross-ios-build (nightly, x86_64-apple-ios)	19s
bare-cross-build (nightly, x86_64-unknown-haiku)	27s
windows-test (nightly, i686-pc-windows-gnu)	58s
native-test (nightly, ubuntu-latest)	12s
cross-ios-build (stable, aarch64-apple-ios)	11s
bare-cross-build (nightly, x86_64-unknown-openbsd)	27s
windows-test (stable, x86_64-pc-windows-gnu)	1m 15s
native-test (nightly, windows-latest)	27s
cross-ios-build (stable, x86_64-apple-ios)	13s
bare-cross-build (nightly, x86_64-unknown-redox)	27s
windows-test (stable, i686-pc-windows-gnu)	1m 15s
native-test (nightly, macOS-latest)	17s
bare-cross-build (nightly, x86_64-fuchsia)	27s
native-test (stable, ubuntu-latest)	14s
native-test (stable, windows-latest)	26s
bare-cross-build (nightly, wasm32-unknown-unknown)	25s
native-test (stable, macOS-latest)	14s
native-test (1.56.0, ubuntu-latest)	1m 45s
native-test (1.56.0, windows-latest)	1m 32s
native-test (1.56.0, macOS-latest)	1m 45s
	14m 35s

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