[pickers] Fix toolbar on the new range pickers

[flaviendelangle]

Fixes #6958 (comment)

We did not pass the props to switch between the start and the end date to the toolbar

Changelog

Breaking changes

• The currentlySelectingRangeEnd / setCurrentlySelectingRangeEnd props on the Date Range Picker toolbar have been renamed to rangePosition / onRangePositionChange.

   const CustomToolbarComponent = props => (
     <div>
  -    <button onChange={() => props.setCurrentlySelectingRangeEnd('end')}>Edit end date</button>
  +    <button onClick={() => props.onRangePositionChange('end')}>Edit end date</button>
  -    <div>Is editing end date: {props.currentlySelectingRangeEnd === 'end'}</div>
  +    <div>Is editing end date: {props.rangePosition === 'end'}</div>
     </div>
   )
   <DateRangePicker
     components={{
       Toolbar: CustomToolbarComponent
     }}
   />

[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	618.2	958.8	763	765.32	134.25
Sort 100k rows	ms	593.5	1,102.2	816.6	846.66	161.993
Select 100k rows	ms	214.7	300	227.5	247.84	33.932
Deselect 100k rows	ms	136.2	271.9	208.3	209.24	43.649

Generated by 🚫 dangerJS against 77673d5