[MaterialDatePicker] [MaterialTimePicker] Provide a widget that allows the user to select a calendar date, and optionally a time

Is your feature request related to a problem? Please describe.
I haven't been able to find a way to add a view to the MaterialDatePicker that will allow users to switch to time and vice versa. Not all user cases are the same and the current MaterialDatePicker and MaterialTimePicker are not helping me to achieve my user requirements. My app might have multiple date/time fields. These are represented by text field in a display state (not focusable - users can not type a date and/or time). The purpose is to minimize data entry errors and maximizes efficiency.

Describe the solution you'd like

1. An inline date/time picker will be best. I know this not something that will happen overnight but this will be the preferable experience
   OR
2. Expose the HeaderToggle accessory. This by default can be the switch from the calendar to input calendar or it can be styled and used to switch from the datepicker to the timepicker.

This screen below shows what I need to achieve from the design point of view.

Design Screen

Describe alternatives you've considered
Expose the neutral button in the fragment that hosts the picker. This will allow to switch from date to time and vice versa

Additional context
Provide a widget that allows the user to select a calendar date, and optionally a time.

iOS Screen

Non vengono indicati file, test o punti di ingresso. Inizia esaminando le API esistenti di MaterialDatePicker e MaterialTimePicker, incluse le alternative HeaderToggle e neutral-button descritte qui. Per considerarlo completato sarebbero necessari un design concordato e un widget che supporti la selezione di una data di calendario con la selezione opzionale dell’ora e il passaggio dall’una all’altra.