[DataGrid] Fix theme styleOverrides for actionsCell and actionsCellItem

[cherniavskii]

Fixes #7619

[mui-bot]

	Messages
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These are the results for the performance tests:

Test case	Unit	Min	Max	Median	Mean	σ
Filter 100k rows	ms	648.3	1,052.6	656.7	852.9	169.956
Sort 100k rows	ms	781.3	1,191.4	1,191.4	969.14	157.624
Select 100k rows	ms	217.2	405.8	267	284.9	68.745
Deselect 100k rows	ms	216.7	337.1	261.5	264.28	40.256

Generated by 🚫 dangerJS against 1b2bb39

[cherniavskii]

Without it, the styles aren't applied to the elements because they're outside of grid DOM tree

[cherniavskii]

Noticed that booleanCell was missing here. There's probably a lot more of those.

[cherniavskii]

I wonder if we can automate this instead of adding each one manually.
Some of the classes use &. because they're applied to the root element, others use & . (notice the space) because they're not applied to the root element.
But still, we can do something like this:

overridesResolver: (props, styles) => {
  return Object.keys(gridClasses).map(key => {
    const prefix = isRootClassName ? '&' : '& ';
    return { [`${prefix}.${gridClasses[key]}`]: styles[key] }
  });
}

[github-actions]

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