Avoid forcing wxYield() after wxUIActionSimulator::MouseMove() in wxGTK.

Yield (for input events only) inside this function itself instead of forcing
all the code using this function to call wxYield() after it as otherwise the
mouse position change is not taken into account by the subsequent simulated
events.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74328 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Better fix for duplicate wxContextMenuEvent generation under MSW.

Fix the bug with multiple wxContextMenuEvent being generated for a single
WM_CONTEXTMENU without breaking context menus for wxTextCtrl (and all the
other native controls). Do this by ensuring that WM_CONTEXTMENU is still
passed to DefWindowProc() if we don't process it instead of just being eaten
completely in any case.

Also add a unit test checking for this bug to ensure it stays fixed.

See #13683.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74329 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775