feat: add `const ONE` #1048

Job	Run time
Docs	58s
Feature checks	1m 19s
Clippy	42s
Cargo deny check	17s
Fmt	12s
test (stable, --no-default-features)	1m 19s
test (stable)	1m 17s
test (stable, --all-features)	2m 11s
test (beta, --no-default-features)	1m 36s
test (beta)	1m 34s
test (beta, --all-features)	2m 27s
test (nightly, --no-default-features)	1m 28s
test (nightly)	1m 27s
test (nightly, --all-features)	2m 17s
test (1.65, --no-default-features)	2m 15s
test (1.65)	2m 21s
Accept	1s
	23m 41s

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