Materials: Change display of Quantity values

The default display type of quantity objects is fixed point resulting
in insufficient accuracy when changing unit systems, or when the values
are small. This fix changes the default format from 'Fixed' to the more
apt 'Default' format. This allows the displayed values to scale as
appropriate.

Fixes #18149

src/Mod/Material/App/MaterialValue.cpp

@@ -311,6 +311,11 @@ QString MaterialValue::getYAMLString() const
     return yaml;
 }
 
+const Base::QuantityFormat MaterialValue::getQuantityFormat()
+{
+    return Base::QuantityFormat(Base::QuantityFormat::NumberFormat::Default, PRECISION);
+}
+
 //===
 
 TYPESYSTEM_SOURCE(Materials::Material2DArray, Materials::MaterialValue)