[MaterialDatePicker][MaterialTimePicker] Support Fragment Result API

Nobody has claimed this yet.

**Is your feature request related to a problem? Please describe.**

The current API of both `MaterialDatePicker` and `MaterialTimePicker` only supports listeners, such as `MaterialTimePicker.addOnNegativeButtonClickListener(listener)`, which unfortunately do not persist across configuration changes.

**Describe the solution you'd like**

Both `MaterialDatePicker` and `MaterialTimePicker` should support [Fragment Result API](https://developer.android.com/guide/fragments/communicate#fragment-result) so that the dialogs work properly even after a configuration change has occurred.

**Describe alternatives you've considered**

Both classes are final so adding this behavior ourselves is not possible.

I also considered extracting the `Dialog` logic and creating a `DialogFragment` myself so that we can set Fragment results.

**Additional context**

Because of this oversight, we decided not to use the `MaterialDatePicker` because it can not be implemented reliably. We continue to use `android.app.DatePickerDialog` which extends `AlertDialog` so that we can wrap it in a `FragmentDialog` which allows us to implement Fragment Result API ourselves.

Start with the MaterialDatePicker and MaterialTimePicker listener APIs and the linked Android Fragment Result API documentation. Define how each dialog exposes results across configuration changes, then verify that both picker types retain and deliver those results after recreation.

Written by the indexing model from the issue text.