Add wxNumberEntryDialog default ctor and Create().

Allow creating wxNumberEntryDialog in 2 steps, as most of the other classes.

Closes #15769.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75408 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775