[NUI] Fix Picker's HeightSpecification

[NUI] Fix Picker's HeightSpecification

Previously, HeightSpecifications of Picker, DatePicker, TimePicker are
MatchParent.
So the Pickers' SizeHeights are calculated based on their parent's
SizeHeight.
This causes the recursive size calculation problem if Picker's parent
has WrapContent HeightSpecification. (e.g. Dialog)

Now, the Pickers' SizeHeights are set in DefaultThemeCommon as follows.
Picker's SizeHeight is set in DefaultThemeCommon.
DatePicker's Pickers SizeHeights are set in DefaultThemeCommon.
TimePicker's Pickers SizeHeights are set in DefaultThemeCommon.

Therefore, Picker does not need to have MatchParent HeightSpecification.