The OSL image compilation step needed to be taught about the new UVTILE
format for UDIM textures.

A small missing feature from OIIO[1] means this is a bit uglier than it
needs to be. Once we update to a version of OIIO with the fix we can
remove the string replace part.

I'd like to checkin tests with this as well. However, I noticed that
UDIMs in general behave differently with OSL due to the clipping mode
seemingly not working?

Tests:

Tests OSL using <UVTILE> and with tiles that do not start at 1001

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[1] https://github.com/OpenImageIO/oiio/commit/35cb6a83e28d77bd9eb30e153abd9df4248863c5