nuke: adding extract thumbnail settings 3.10

[jakubjezek001]

Brief description

Thumbnail can be passed from rendered with bypassed baking

Description

Thumbnail was not correctly identifying existing path. It was pushing the process to re-render thumbnail from node tree instead of getting rendered frame. Also we didn't have toggles for baking process, so those were included now too.

Testing notes:

1. open testing workfile on testing project
2. go to settings on your project project_settings/nuke/publish/ExtractThumbnail/bake_viewer_process
3. set toggles as shown on picture
   
4. publish as local or use rendered images
5. see that thumbnail plugin will create read node (it is very quick process so be mindfull :D)
6. check rendered thumnail in ftrack and notice that gamma is dark (in case your render was set to linear space)

notes

3.10 alternative from #3148

[ynbot]

Task linked: OP-3135 Nuke: thumbnail gamma issue