add specialized `Buf::chunks_vectored` for `Take` #817

Job	Run time
loom	19s
minrust	1m 42s
miri	3h 28m 47s
cross (i686-unknown-linux-gnu)	32s
cross (armv7-unknown-linux-gnueabihf)	32s
nightly	1m 0s
panic=abort tests	28s
cross (powerpc-unknown-linux-gnu)	37s
rustfmt	12s
cross (powerpc64-unknown-linux-gnu)	32s
stable (ubuntu-latest)	1m 24s
cross (wasm32-unknown-unknown)	13s
tsan	1m 20s
stable (macos-latest)	1m 28s
stable (windows-latest)	2m 52s
Publish Documentation	0s
	3h 41m 58s

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