feat(timepicker): Allow mat-timepicker to work with other controls different than input[matTimepicker]

[robmv]

Feature Description

I have a custom time input component that is a wrapper for two input fields and a button (for AM/PM or the localized version of those):

This custom component can't be currently integrated with <mat-timepicker> because it explicitly requires a MatTimepickerInput. <mat-timepicker> could instead requires an common interface that any control must implement in order to be able to interact with the picker.

Internally this is already happening for MatTimepickerInput because it implements a getOverlayOrigin() method in order to satisfy the picker requirements. This could be extended to other methods and allow other controls to integrate with the picker.

Use Case

Be able to use <mat-timepicker> without an input[matTimepicker] but with other custom controls.