[MSPAINT] Support converting to black and white (#5554)

- Add ImageModel::IsBlackAndWhite and ImageModel::PushBlackAndWhite
  helper functions.
- Add CAttributesDialog::m_bBlackAndWhite.
- If IDD_ATTRIBUTESRB4 is checked, then make
  the bitmap black and white.
- Add IDS_LOSECOLOR to show message.
CORE-19094

base/applications/mspaint/dialogs.h

@@ -64,6 +64,7 @@ public:
 public:
     int newWidth;
     int newHeight;
+    BOOL m_bBlackAndWhite;
 };
 
 class CStretchSkewDialog : public CDialogImpl<CStretchSkewDialog>