refactor: Move from Lazy to OnceCell

[epage]

This is prep for exploring a way to drop once_cell without an MSRV bump

[coveralls]

Pull Request Test Coverage Report for Build 15172726916

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 30 of 30 (100.0%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 28.571%

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Totals
Change from base Build 15172477243:	-0.1%
Covered Lines:	326
Relevant Lines:	1141

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💛 - Coveralls