Dialogs not visible on idioms other than Phone or Tablet

## 🐛 Bug Report
A customer lamented the fact that dialog messases were not visible on its Android phone.
Doing some research we found that due to a scaling he applied to its phone text, `OnIdiom` is not behaving correctly, detecting its phone as `Desktop` or `TV` whena using a small font.

He's using a Redmi Note 8T and I couldn't reproduce this behaviour on other Android devices.
I'm filling in an Issue to Xamarin Forms too for the problem with `OnIdiom`, but to solve this problem it would be enough to handle all the idioms inside [MaterialSizes](https://github.com/Baseflow/XF-Material-Library/blob/58089c4cf221ae27e98e03979b8a7da7d4008acf/XF.Material/FormsResources/MaterialSizes.xaml#L12)

### Reproduction steps
On a Redmi Note 8T change the font size to something smaller that the `Small` option.

### Configuration

**Version:** 1.7.5

**Platform:**
- [ ] :iphone: iOS
- [x] :robot: Android
- [ ] :checkered_flag: WPF
- [ ] :earth_americas: UWP
- [ ] :apple: MacOS
- [ ] :tv: tvOS
- [ ] :monkey: Xamarin.Forms