support vectored IO #2256

Job	Run time
codegen	17s
cargo-deny check	26s
Interop Tests (ubuntu-latest)	23s
check (ubuntu-latest)	46s
Interop Tests (macOS-latest)	57s
Check MSRV	3m 42s
check (macOS-latest)	4m 16s
rustfmt	8s
Interop Tests (windows-latest)	2m 16s
check (windows-latest)	3m 18s
test (ubuntu-latest)	5m 31s
test (macOS-latest)	3m 56s
Check unused dependencies (ubuntu-latest)	3m 54s
test (windows-latest)	5m 33s
Check unused dependencies (macOS-latest)	7m 27s
Check unused dependencies (windows-latest)	11m 4s
	53m 54s

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