fix(dtype): dtype scalar set_retain_dtype supports bool

GitOrigin-RevId: aafd378e1b958c37d21c64c01bf9476f8d590c8a

src/core/impl/dtype.cpp

@@ -209,6 +209,7 @@ typename ctype_enable_if<ctype>::type DTypeScalar::set_retain_dtype(ctype val) {
     }
         MEGDNN_FOREACH_COMPUTING_DTYPE(cb)
         MEGDNN_FOREACH_QUANTIZED_DTYPE(cb)
+        cb(dt_bool);
 #undef cb
         default:
             mgb_throw(ConversionError, "can not assign to dtype %s", m_dtype.name());