buffer: make methods work on Uint8Array instances #645

Job	Run time
Build slim tarball	1m 28s
aarch64-linux: with shared libraries	23m 41s
x86_64-linux: with shared libraries	28m 14s
x86_64-darwin: with shared libraries	45m 45s
aarch64-darwin: with shared libraries	29m 6s
	2h 8m 14s

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