Fix #119586: Vertex paint mode crash after converting color attribute

Converting a color attribute to a non-color domain or type causes vertex
paint mode to try to change the attribute even though it's unsupported.
That leads to a crash here and unpredictable behavior elsewhere.

This PR modifies some poll functions to check for the proper domain and
data type before continuing. Even if converting an attribute properly
updates the active color attribute, we can still run into situations where
the active name references an attribute with incorrect metadata.

@@ -597,6 +597,24 @@ void smooth_brush_toggle_on(const bContext *C, Paint *paint, StrokeCache *cache)
 /** \} */
 }  // namespace blender::ed::sculpt_paint::vwpaint
 
+static bool attribute_supported(const std::optional<bke::AttributeMetaData> meta_data)