Use the same console event loop in wxBase and wxCore in wxMSW.

Refactor the console event loop code into separate files to untangle it from
the GUI version and ensure that it doesn't depend on the GUI at all. It can
now be defined in the base library and simply reused by the core one.

This also makes the console event loop usable for other ports under Windows,
e.g. wxGTK.

Closes #14426.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72008 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775