chore: `IntoImplementation` type alias #6256

Job	Run time
pytest-38 (3.8, windows-latest)	1m 10s
pytest-38 (3.8, ubuntu-latest)	48s
pytest-full-coverage (3.11, ubuntu-latest)	5m 0s
pytest-full-coverage (3.13, ubuntu-latest)	2m 50s
pytest-windows (3.10, windows-latest)	12m 1s
pytest-windows (3.12, windows-latest)	3m 56s
	25m 45s

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