Improved OSL interoperability

The color4, color2, vector4, vector2, and matrix33 are now supported as output types of OSL shaders when connected to Arnold shaders. Additionaly, Arnold shaders that output RGBA or Vector2 types can now be directly connected to OSL shader color4 and vector2 input parameters. Those features make it easier to mix Arnold and MaterialX standard library shader nodes. (ARNOLD-13989, ARNOLD-14692)