feat: add `copy_*e_to_slice` family #964

Job	Run time
Feature checks	34s
Docs	49s
Cargo deny check	23s
Fmt	13s
Clippy	51s
test (stable, --no-default-features)	56s
test (stable)	58s
test (stable, --all-features)	2m 5s
test (beta, --no-default-features)	1m 2s
test (beta)	1m 3s
test (beta, --all-features)	2m 21s
test (nightly, --no-default-features)	55s
test (nightly)	52s
test (nightly, --all-features)	1m 53s
test (1.65, --no-default-features)	15s
test (1.65)	15s
Accept	0s
	15m 25s

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