chore: `IntoImplementation` type alias #6244

Job	Run time
pytest-38 (3.8, windows-latest)	1m 29s
pytest-full-coverage (3.11, ubuntu-latest)	4m 57s
pytest-38 (3.8, ubuntu-latest)	48s
pytest-windows (3.10, windows-latest)	12m 25s
pytest-full-coverage (3.13, ubuntu-latest)	2m 50s
pytest-windows (3.12, windows-latest)	3m 46s
	26m 15s

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