Remove unnecessary mondrian.{ico,xpm} files from samples directory.

Remove unnecessary mondrian.{ico,xpm} files from samples directory.

Standardize on using sample.rc and sample icon in all the samples, it was
confusing that some of them used it and other didn't, without any apparent
logic.

Remove the now unnecessary icon files, including the dialogs sample icon which
seemed to be corrupted (this closes #11146).

Also replace multiple OS/2 resource files with a single one in the sample
directory. The OS/2 projects/makefiles would need to be updated to use them.

Remove dialogs sample icon.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64645 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775