fix: Fix Grid scrollToCell method not working if a scrollTop prop is defined, which is usual for WindowScroller usage

[driskell]

• The existing test suites (npm test) all pass
• For any new features or bug fixes, both positive and negative test cases have been added
• N/A For any new features, documentation has been added
• N/A For any documentation changes, the text has been proofread and is clear to both experienced users and beginners.
• Format your code with prettier (yarn run prettier).
• Run the Flow typechecks (yarn run typecheck).

NOTE: AI was used to help build the test. The fix is completely my own.

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This fixes #1893

The issue is that WindowScroller requires you to pass scrollTop prop. And in React 16.4+ getDerivedStateFromProps calls on every prop AND state change. So what happens is that once a scrollToCell method is called and everything updated, the final update before componentDidUpdate kicks in to update scroll position causes getDerivedStateFromProps to call but that then detects scrollTop and resets everything.

The fix is for getDerivedStateFromProps to only obey scrollTop/scrollLeft when they change.

Test added that fails without the fix.