refactor: splitting up of NonlinearSolve #244

Job	Run time
test (Core, 1.10, ubuntu-latest)	15m 26s
test (Core, 1.10, macos-latest)	12m 38s
test (Core, 1.10, windows-latest)	20m 10s
test (Core, 1, ubuntu-latest)	27m 54s
test (Core, 1, macos-latest)	18m 4s
test (Core, 1, windows-latest)	33m 50s
test (Downstream, 1.10, ubuntu-latest)	8m 9s
test (Downstream, 1.10, macos-latest)	5m 4s
test (Downstream, 1.10, windows-latest)	11m 39s
test (Downstream, 1, ubuntu-latest)	18m 4s
test (Downstream, 1, macos-latest)	15m 2s
test (Downstream, 1, windows-latest)	21m 49s
test (Wrappers, 1.10, ubuntu-latest)	9m 16s
test (Wrappers, 1.10, macos-latest)	5m 47s
test (Wrappers, 1.10, windows-latest)	12m 49s
test (Wrappers, 1, ubuntu-latest)	19m 15s
test (Wrappers, 1, macos-latest)	11m 39s
downgrade (1.10, Core)	15m 45s
test (Wrappers, 1, windows-latest)	25m 42s
downgrade (1.10, Downstream)	8m 21s
downgrade (1.10, Wrappers)	10m 17s
	5h 26m 40s

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