Blender Git Loki

BLI_task: tweak default chunk size for `BLI_task_parallel_range()`.

Previously we were setting it to 1 (aka no 'chunking'), to follow
previous behavior. However, this is far from optimal, especially with
CPUs that can have tens of threads nowadays.

Now taking an heuristic approach (inspired from the one already existing
for `BLI_task_parallel_listbase()`, which tries to guesstimate best
chunk sizes based on several factors (amount of threads/parallel tasks,
total number of items, ...).

Think this is a reasonable base ground, more optimization here would of
course be possible.

Note that code that was already explicitely settings some value here
won't be affected at all by that change.