Blender Git Loki

Python/Context: do not allow any UI context access from threads like render
or baking. This basically means you will only have access to bpy.data and
bpy.context.scene, not current window, active object, etc, as those are not
thread safe anyway and were likely to cause issues already.

This fixes #30858, where the UI would lose buttons due to context getting
corrupted when editing objects in pre/post render or using luxrender. The
context access they did (indirectly) was only using the current scene or
data so they still work.