feat: add `copy_*e_to_slice` family #970

Job	Run time
Docs	51s
test (stable, --no-default-features)	57s
Cargo deny check	27s
test (stable)	57s
Clippy	50s
Feature checks	25s
test (stable, --all-features)	2m 4s
test (beta, --no-default-features)	1m 3s
Fmt	13s
test (beta)	1m 2s
test (beta, --all-features)	2m 22s
test (nightly, --no-default-features)	1m 0s
test (nightly)	57s
test (nightly, --all-features)	1m 51s
test (1.65, --no-default-features)	17s
test (1.65)	21s
Accept	0s
	15m 37s

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