Allow partially erasing date by keyboard without moving rest of date string

[Talal916]

Is your feature request related to a problem? Please describe.
Deleting characters in the middle of a date/time/datetime string through the keyboard results in the rest of the string shifting left.

https://material-ui-pickers.dev/demo/datepicker

Describe the solution you'd like
I'd like to able to edit parts of the date and time without the rest of the date/time/datetime being affected. This is the standard behavior for most datepickers and the keyboard pickers used by Material-UI result in unexpected behavior for users.

This is a demo of the desired behavior, using the native picker.
https://material-ui.com/components/pickers/

[Talal916]

Here's another example of the current behavior being unpleasant

[croraf]

Yes, this is a very bad user experience.

When nothing is selected but cursor is in the field:

• DEL sets the next figure to "_" or the letter representation of the figure ("d", "m", "y"). I don't know if the cursors position should change or stay where it was?
• backspace sets the previous figure to "_" or the letter representation of the figure. The cursor should move 1 figure back.

When some figures are selected then:

• DEL should put all these figures to "_" or letter representation of the figures. Not sure where the cursor position should end?
• backspace should put all these figures to "_" or letter representation of the figures. The cursor should be set to the beginning of the selection.

[dmtrKovalenko]

Already fixed in v4-alpha👨‍🏭