Implement `IoBuf` for `Rc` and `Arc` of `IoBuf` types. (#239) #580

Job	Run time
test (x86_64-unknown-linux-gnu, stable)	4m 39s
test (x86_64-unknown-linux-gnu, nightly)	4m 44s
test (i686-unknown-linux-gnu, stable)	2m 21s
test (i686-unknown-linux-gnu, nightly)	2m 9s
test (aarch64-unknown-linux-gnu, stable)	1m 40s
test (aarch64-unknown-linux-gnu, nightly)	1m 38s
test (armv7-unknown-linux-gnueabihf, stable)	2m 3s
test (armv7-unknown-linux-gnueabihf, nightly)	1m 21s
test (riscv64gc-unknown-linux-gnu, stable)	1m 47s
test (riscv64gc-unknown-linux-gnu, nightly)	1m 39s
test (s390x-unknown-linux-gnu, stable)	2m 14s
test (s390x-unknown-linux-gnu, nightly)	1m 36s
test (x86_64-apple-darwin, stable)	3m 41s
test (x86_64-apple-darwin, nightly)	3m 29s
test (aarch64-apple-darwin, stable)	2m 38s
test (aarch64-apple-darwin, nightly)	2m 31s
test (x86_64-pc-windows-gnu, stable)	4m 9s
test (x86_64-pc-windows-gnu, nightly)	3m 24s
test (x86_64-pc-windows-msvc, stable)	4m 36s
test (x86_64-pc-windows-msvc, nightly)	4m 19s
test (i686-pc-windows-gnu, stable)	5m 37s
test (i686-pc-windows-gnu, nightly)	5m 43s
test (i686-pc-windows-msvc, stable)	3m 42s
test (i686-pc-windows-msvc, nightly)	2m 21s
	1h 14m 1s

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