Arnold 7.0 support

[JenusL]

This update brings support for the following new Arnold features from Arnold 6.2 and 7.0

• OCIO default color manager
• EXR Multipart support
• Denoising imagers:
  • imager_denoiser_noice Arnold Denoiser
  • imager_denoiser_oidn Intel Open Image Denoise
  • imager_denoiser_optix nVidia Optix denoiser
• imager_lens_effects now has Bloom
• imager_tonemap got support for LUTs + UI enhancements
• ignore_imagers render option

Incompatible / Behavior changes

• Default color manager has been changed to use OCIO and default render colorspace has changed to ACEScg.
• GPU settings is now always exported
• use_existing_tx is now handled by Arnold core instead of the SItoA plugin

Bugfixes

• Made Arnold handle if shaders are linkable or not. This made some more parameters linkable that was incorrectly set to not be linkable before.

Build system fixes / changes:

• Easy double-click shortcut to open a dev console in cmd or Windows Terminal (if installed)
• Fixed a deadlock bug in testsuite
• Updated all test suite reference images due to the color manager change making them not pass anymore.

Passes testsuite. This closes #89

[JenusL]

Well there it is. Basic support for Arnold 7. I don't plan to add anything more right now so this can probably be merged now.

[sjannuz]

@JenusL I see you updated all the baseline images, were they all different ?

[JenusL]

@sjannuz All non-greyscale images were different because of the change in render color space to ACEScg, and the default OCIO color manager made a harder "color grade" on the output images. I think it was around 40 tests that failed, but the rest had slight color differences in them probably right below the diff threshold. So I thought it was easiest to just update them all. I carefully went through them to see so nothing else but the colors where different. So all tests passed.