Bug 41353 - Move PNGs to correct folder

Some PNGs for the org.eclipse.debug.ui plugin were stored in the
wrong folder (without the "icons" path segment). They are now moved
to the org.eclipse.debug.ui/icons/... folder.

Change-Id: I7591373ae3897f5426e240e945f9a78b3c3ad297
Signed-off-by: Matthias Becker <ma.becker@sap.com>