Add min width/height to template styles of select controls

[rachelkang]

Description of Change

A min size of 44x44 is required for the accessibility of interactive controls, particularly on Android.
Therefore, a min width/height was set in template styles for select controls:

• Button
• ImageButton
• CheckBox
• RadioButton
• Editor
• Entry
• Picker
• DatePicker
• TimePicker

Interactive controls not addressed here will be addressed separately (i.e. SearchView #2956, IndicatorView #10404)

Issues Fixed

Fixes #2957

[jsuarezruiz]

In Xamarin.Forms this was managed at the Renderer level, should some controls require a minimum at the Handlers level?

[AmrAlSayed0]

While it's "good" for accessibility to have clickable controls be 44 px or larger, it should stay relatively easy to override that for people who really want to override that behavior. In this case, setting the minimum height/width on the control itself or overriding the global styles would be enough instead of subclassing the handler which much harder for most users