[TIMOB-28427] Android: Add "borderStyle" and "hintText" properties to Ti.UI.Picker

*Summary:* On Android, if we display the picker as a read-only text field, then we should also add properties [borderStyle](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.UI.TextField-property-borderStyle) and [hintText](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.UI.TextField-property-hintText) that work similarly to Ti.UI.TextField. *Drop-Down Picker Support:* When a Ti.UI.Picker} is set up as [PICKER_TYPE_PLAIN](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.UI-property-PICKER_TYPE_PLAIN) (the default) and its [useSpinner](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.UI.Picker-property-useSpinner) property is set {{true, then the picker is shown as a drop-down field. Titanium currently shows this as a borderless view using the Java Spinner class as shown here... https://developer.android.com/guide/topics/ui/controls/spinner It should be changed to use a material [TextInputLayout](https://developer.android.com/reference/com/google/android/material/textfield/TextInputLayout) and [MaterialAutoCompleteTextView](https://developer.android.com/reference/com/google/android/material/textfield/MaterialAutoCompleteTextView) so that it will look like the below. This follows Google's material guidelines and Google's own apps. !Picker-DropDown-Border-Light.png|thumbnail! !Picker-DropDownClicked-Border-Light.png|thumbnail! !Picker-DropDown-Border-Dark.png|thumbnail! !Picker-DropDownClicked-Border-Dark.png|thumbnail! *Compact Date/Time Picker Support:* When we add support for [DATE_PICKER_STYLE_COMPACT](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.UI.iOS-property-DATE_PICKER_STYLE_COMPACT) via [TIMOB-28426], then the picker will appear as a read-only text field that shows a selection dialog when tapped on. The border style should be configurable to match the border style used by Ti.UI.TextField views. !Picker-Date-Border-Light.png|thumbnail! !Picker-Date-Border-Dark.png|thumbnail! !Picker-Time-Border-Light.png|thumbnail! !Picker-Time-Border-Dark.png|thumbnail!