chore: prepare v1.6.0 #585

Job	Run time
miri	10m 11s
loom	1m 0s
minrust	1m 1s
cross (i686-unknown-linux-gnu)	38s
cross (armv7-unknown-linux-gnueabihf)	39s
nightly	2m 1s
cross (powerpc-unknown-linux-gnu)	36s
rustfmt	15s
stable (ubuntu-latest)	1m 17s
cross (powerpc64-unknown-linux-gnu)	38s
stable (macos-latest)	1m 38s
cross (wasm32-unknown-unknown)	14s
tsan	1m 26s
stable (windows-latest)	2m 14s
Publish Documentation	47s
	24m 35s

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