Fix setting frame icon when using non-standard icon sizes in wxMSW.

Fix setting frame icon when using non-standard icon sizes in wxMSW.

Set the closest (and larger, if possible) icon if the icon of exactly the
system icon size is not available. This fixes setting the icons when using
custom DPI settings under MSW as the standard icon size may be different from
the standard 32*32 in this case.

This also improves wxIconBundle::GetIcon() to make its behaviour when the icon
with exactly the given size is not found more flexible as a side effect.

Closes #13891.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70455 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775