Provide shorter synonyms for wxEVT_XXX constants.

Use the same short names as are used by the event table macros for the event
type constants themselves. This makes them much more comfortable to use, e.g.
Bind(wxEVT_BUTTON) compared to Bind(wxEVT_COMMAND_BUTTON_CLICKED).

The old long names are still kept for backwards compatibility and shouldn't be
removed as it doesn't really cost anything to continue providing them, but all
new event types should only use the short versions.

Closes #10661.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73850 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775