feat: add `copy_*e_to_slice` family #965

Job	Run time
Docs	49s
Feature checks	19s
Clippy	53s
Cargo deny check	24s
Fmt	17s
test (stable, --no-default-features)	1m 18s
test (stable)	1m 2s
test (stable, --all-features)	2m 3s
test (beta, --no-default-features)	1m 3s
test (beta)	1m 3s
test (beta, --all-features)	2m 14s
test (nightly, --no-default-features)	59s
test (nightly)	57s
test (nightly, --all-features)	1m 52s
test (1.65, --no-default-features)	23s
test (1.65)	16s
Accept	0s
	15m 52s

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