[wip] Add structured parameter #21577

Job	Run time
pytestmypy (ubuntu-latest, 3.12, false)	9m 13s
pytestmypy (ubuntu-latest, 3.11, true)	8m 8s
pytestmypy (windows-latest, 3.12, false)	23m 11s
pytestmypy (ubuntu-latest, 3.13, false)	9m 35s
pytestmypy (ubuntu-latest, 3.14, false)	8m 20s
	58m 27s

Provide feedback