[DateRangePicker] Change open trigger to onMouseDown

[LukasTy]

Created from #9386 (comment)

Range pickers do open when clicked on the input element rather than the open button as the regular pickers.
The input element has its own behavior when it is moused down (the input focuses and the active section is selected), but the opening of the picker happens only when the click action is finished on the input.

The proposal is to use onMouseDown as the trigger to opening the range picker popper to increase the responsiveness and avoid this double effect of one behavior when input is moused down and another when the click is completed.

[LukasTy]

#14786 should remove this problem from the new default variant - single input range field.
Re-groom this issue after #14786 is done to assess the state with multi-input range field.