Handle tests. Not all dispose are removed as there explicit checks in
multiple components to not allow disposed colors.

Change-Id: I3036ff1ae616191ea470b4ce65f89b2d4a546c68
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.swt/+/185425
Tested-by: Platform Bot <platform-bot@eclipse.org>
Reviewed-by: Alexander Kurtakov <akurtako@redhat.com>