Blender Git Loki

Bump maximum threads number to 1024

This commit contains all the changes required for most optimal maximum threads
number bump. This is needed to avoid possibly unneeded initialization or data
allocation on systems with lower threads count.

TODO: Still need to review arrays in render data structures from render_types.h,

P.S. We might remove actual bump of max threads from this patch, so when we'll
be applying the patch we can do all the preparation work and then do actual
bump of max threads.

Reviewers: mont29, campbellbarton

Reviewed By: mont29, campbellbarton

Maniphest Tasks: T43306

Differential Revision: https://developer.blender.org/D1343