[pickers] Add overrides to PickersArrowSwitcher

[m4theushw]

Preview: https://deploy-preview-4672--material-ui-x.netlify.app/x/react-date-pickers/date-picker/

An example for #4669

My goal was to only restore the capability to provide overrides via the theme and add meaningful class names. I didn't add the classes prop.

Some components have "private" class names. Do you agree to make them public? In the DataGrid every new class is public.

mui-x/packages/x-date-pickers/src/CalendarPicker/PickersSlideTransition.tsx

Line 18 in 0d8a55d

const classes = generateUtilityClasses('PrivatePickersSlideTransition', [

Before:

After:

[mui-bot]

These are the results for the performance tests:

Test case	Unit	Min	Max	Median	Mean	σ
Filter 100k rows	ms	258.5	595.9	498.6	444.34	147.424
Sort 100k rows	ms	473.9	927.9	639.5	679.48	149.619
Select 100k rows	ms	109	245.8	137.8	158.64	48.301
Deselect 100k rows	ms	99.2	209.1	178.4	155.88	37.255

Generated by 🚫 dangerJS against 474cba5

[oliviertassinari]

The changes seem to match with what we do on the rest of the codebase, especially in Material UI.

Some components have "private" class names. Do you agree to make them public? In the DataGrid every new class is public.

Usually, developers ask to be able to customize everything. I think that the only cases when a class name should stay private is if we don't envison a way to use it for customization, or if either is a better way to achieve the same customization.

[flaviendelangle]

Usually, developers ask to be able to customize everything. I think that the only cases when a class name should stay private is if we don't envison a way to use it for customization, or if either is a better way to achieve the same customization.

Or if we want to be able to change them before the next major
I never saw it happen though

[m4theushw]

I would say to keep only classes of the XXXTransition components as private, but even these the users might want to customize. For instance, if I want to override the animation duration or easing only with CSS is possible. It seems that the path is to make every class public.