Merge branch 'blender-v2.82-release'

Cleanup: factorize collection handling in libquery code.

Both actual Collection datablocks and the horrible master collection
should share the same code (there were already some differences,
although probably not critical, but some callbacks from
scene->master_collection did not have the 'not self' flag...).

Cleanup: remove dead code in full scene copy/make single users area.

Fix T73170: New Scene -> "Full Copy" Crashes Blender.

rBac723db57fd8ba5 makes proper remapping of all pointers in Scene...
including the object pointers of bases in ViewLayers.

Using `BKE_main_collection_sync_remap()` makes sense here anyway
(compared to `BKE_main_collection_sync()`, it additionally clears caches
in ViewLayers and Collections), this whole code makes a lot of
remapping.

Note that I do not really understand *why* that was working OK
before rBac723db57fd8ba5. I.E. *why* not remapping at all ViewLayers'
base object pointers seemed to be OK...

This whole collection/viewlayer caching is very hard to follow, and
really needs a full rework at some point (just as much as ID copying
code in general, and scene copying code in particular, in fact).

Cleanup of previous rBac723db57fd8ba5 commit.

Simplify a bit, and remove some now redundant remappings.

As a side note, rBac723db57fd8ba5 actually also fixed some unreported
issues (missing remappings to new objects/collections in new copied
scene, that were not previously handled by the 'custom' code).

There are almost certainly still some missing remappings around,
though...

Fix memory leak when full-copying a scene after recent changes.

Once again, am not exactly sure why that was working before, and not
anymore - but in any case, doing that kind of update here is not only
useless (since we have to do it at the end of the whole
collections/objects duplication and remapping anyway), it is also rather
dangerous, as collections are currently in rather invalid states at that
point of the code...

Note that in ideal world, `BKE_main_collection_sync()` & co would be
lazy (setting only a flag, then code actually needing this to be valid
again should call some sort of `BKE_main_collection_sync_ensure()`).
Then we would not have to worry about such things (and we'd get nice
performance improvements in some cases, also in main remapping code,
etc.).

Food for some refactoring, some day...

Merge branch 'blender-v2.82-release'

Fix T72887: Outliner crashes when after undo of some linking operation.

Outliner tree building code was not handling properly empty libraries
(i.e. Lib datablocks in our bmain which have no used actual data
anymore).

Main issue here is unclean states of indirect hierarchies of linking
involving several libraries after undo operation.

This is not a critical issue though, just annoying and untidy.

Merge branch 'blender-v2.82-release'

Fix T73125: Crash when opening a file containing a Line Style.

Dummy typo in rB2e6159a4.