[BUG] inconsistent results of ImageBuf colorconvert in built without OCIO and with OCIO.

[ssh4net]

Describe the bug

Inconsistent results of ImageBuf colorconvert() when OpenImageIO built without OpenColorIO and with OpenColorIO. Quite common case when oiiotools usually building in vcpkg in a minimal configuration openimageio[core,oiiotools]. Or with OCIO support openimageio[core,oiiotools,opencolorio].

As result any example from OIIO documentation give a different resul when OCIO enabled or disabled. That happen because default color space for OCIO is ACES-AP1 (ACEScg) and no "linear" color space defined.

Libraw plugin in same time use "standard" naming for sRGB, linear, aces, etc. And "linear" color space are alias for sRGB LInear.

Issue i feel is more complicated due to OCIO forcing to use it own conventions and ignoring the facts that a lot of work spaces still understand sRGB as default color space and Linear is a "sRGB Linear". So any fix will be just a patch to fix OCIO issue when actual OIIO code is correct.

To Reproduce

oiiotool photo.jpg --colorconvert sRGB linear -o output.exr

depend on OCIO result will be a sRGB Linear or ACEScg exr file. Same in other direction.

oiiotool photo.jpg --colorconvert linear sRGB -o output.exr with OCIO input will be treat as ACEScg and sRGB result will be incorrect.