Picker - enhance modalProps merging in useNewPickerProps

[adids1221]

Description

When passing customPickerProps with modalProps the default modal props are getting overridden.
This pr fixing the issue, by merging the default props with the user custom modal props to not override the animation unless the user passed the relevant props.

Snippet:

 <Picker
        placeholder="Favorite Language"
        value={language}
        onChange={item => setLanguage(item)}
        items={options}
        customPickerProps={{
          modalProps: {}
        }}
      />

Changelog

Picker merging default modal props with the user custom modal props.

Additional info

None