chore: prepare v1.6.0 #584

Job	Run time
minrust	1m 18s
loom	1m 2s
miri	9m 52s
cross (i686-unknown-linux-gnu)	37s
nightly	1m 59s
cross (armv7-unknown-linux-gnueabihf)	41s
rustfmt	12s
cross (powerpc-unknown-linux-gnu)	38s
stable (ubuntu-latest)	1m 16s
stable (macos-latest)	3m 23s
cross (powerpc64-unknown-linux-gnu)	37s
cross (wasm32-unknown-unknown)	14s
stable (windows-latest)	2m 10s
tsan	1m 21s
Publish Documentation	46s
	26m 6s

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