Greyscale option for Standard View Transform

At present, only AGX has a greyscale option in color management. Introducing this to the Standard V iew transform as well would greatly benefit grease pencil artists, as it enables real-time previewing of their art in greyscale.

While a workaround exists involving the viewport compositor and the RGB to BW node, it can be somewhat inconvenient. This method essentially takes over the entire compositor, making it less than ideal for later stages in the creative process. Incorporating a dedicated greyscale preview option within the color management panel would streamline this functionality and enhance the overall user experience.