[pickers] fix to trigger `onChange` when clearing not empty value

[LukasTy]

Fixes #5690

Force trigger an onChange call when clicking clear button with not empty value. Covers case, when date picker has Invalid date due to manual entry, but internally the state is saved as null already.

Simply adding a check in setDate function causes inconsistent behaviour, where simply closing the picker would also reset an invalid value.

[mui-bot]

These are the results for the performance tests:

Test case	Unit	Min	Max	Median	Mean	σ
Filter 100k rows	ms	282.2	561	413.8	396	101.913
Sort 100k rows	ms	500.5	1,117.8	736.7	861.72	218.296
Select 100k rows	ms	199.5	304.2	259.5	257	41.921
Deselect 100k rows	ms	139.6	270.9	176.1	194.28	47.292

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