private boolean isValidIcon(File file) {
			if (!file.exists()) {
				return false;
			}
			try {
				UrlImageIcon icon = new UrlImageIcon(file.getAbsolutePath(), file.toURI().toURL());
				icon.getIconWidth();
				return true;
			}
			catch (Exception e) {
				Msg.showError(this, dropDown, "Invalid Icon File",
					"The file is not a valid icon: " + file.getAbsolutePath());
				return false;
			}

		}
Returns all icons loaded by core Ghidra modules. For this use, we only want to use
icons that are part of a standard distribution because if they are exported, they may
not be available on import. Non-core icons can be used by picking them from the file
system.
@Return all icons loaded by core Ghidra modules
Ghidra/Framework/Docking/src/main/java/docking/options/editor/IconPropertyEditor.java