Fix T71199: Child-parent relationships arent kept after you make instances real.

Comparison function of the of the parent ghash was not fully correct,
could lead to some false positives in some cases...

Fix T70789: Using Remove Single Override breaks file loading (crash).

We only need to refine rna pointer for actual collection properties,
other arrays we handle directly the the appy callback.

Fix T70778: Library Override dissabled after re-instancing same collection in different scene.

Very stupid mistake in own new generic ID lib_link function, that would try
to link ID pointers for all data-blocks, not only those actually needing it.

Fix T70875: Library Override: Clicking an Library Overriden Object crashes Blender.

We also need to rebuild the whole collection/viewlayer object cache
thing when we relink an objector collection in a collection (since it
might be part of a view layer).

Again, usual disclaimer about how inneficient this is currently, needs a
serious refactor to only tag caches as dirty, and actually rebuild the
whole thing on access.

Merge branch 'master' into undo-experiments

Merge branch 'master' into tmp-task-foreach-pool

BLI_task: Add new generic `BLI_task_parallel_iterator()`.

This new function is part of the 'parallel for loops' functions. It
takes an iterator callback to generate items to be processed, in
addition to the usual 'process' func callback.

This allows to use common code from BLI_task for a wide range of custom
iteratiors, whithout having to re-invent the wheel of the whole tasks &
data chuncks handling.

This supports all settings features from `BLI_task_parallel_range()`,
including dynamic and static (if total number of items is knwon)
scheduling, TLS data and its finalize callback, etc.

One question here is whether we should provide usercode with a spinlock
by default, or enforce it to always handle its own sync mechanism.
I kept it, since imho it will be needed very often, and generating one
is pretty cheap even if unused...

----------

Additionaly, this commit converts (currently unused)
`BLI_task_parallel_listbase()` to use that generic code. This was done
mostly as proof of concept, but performance-wise it shows some
interesting data, roughly:
- Very light processing (that should not be threaded anyway) is several
times slower, which is expected due to more overhead in loop management
code.
- Heavier processing can be up to 10% quicker (probably thanks to the
switch from dynamic to static scheduling, which reduces a lot locking
to fill-in the per-tasks chunks of data). Similar speed-up in
non-threaded case comes as a surprise though, not sure what can
explain that.

While this conversion is not really needed, imho we should keep it
(instead of existing code for that function), it's easier to have
complex handling logic in as few places as possible, for maintaining and
for improving it.

Note: That work was initially done to allow for D5372 to be possible... Unfortunately that one proved to be not better than orig code on performances point of view.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D5371

Pool range iter: compute 'static' scheduler chunk size from smallest range.

Computing it from sum of all the ranges is rather stupid and meaning
less, pooled range iterator needs to be at least somewhat dynamic in any
case...

Merge branch 'master' into tmp-task-foreach-pool

BLI_task: Initial implementation of pooled threaded index range iterator.

This code allows to push a set of different operations all based on
iterations over a range of indices, and then process them all at once
over multiple threads.

This is mainly interesting for relatively low amount of individual
tasks, as expected.

E.g. performance tests on a 32 threads machine, for a set of 10
different tasks, shows following improvements when using pooled version
instead of ten sequential calls to `BLI_task_parallel_range()`:

| Num Items | Sequential | Pooled | Speed-up |
| --------- | ---------- | ------- | -------- |
| 10K | 365 us | 138 us | 2.5 x |
| 100K | 877 us | 530 us | 1.66 x |
| 1000K | 5521 us | 4625 us | 1.25 x |

Differential Revision: https://developer.blender.org/D6189