[wpilib] Color: Improve string support (#8403)

Now rgb() and color constants are supported.

Changed from constructor to fromString() factory function to enable
directly returning color constant values.

wpilibc/src/main/python/semiwrap/Color.yml

@@ -168,7 +168,7 @@ classes:
               b:
                 name: blue
           int, int, int:
-          std::string_view:
+      FromString:
       FromHSV:
       HexString:
       operator==: