LibOverride: Silence some more asserts.

Print out messages into console instead when se cannot find expected
data (this is actually normal when source library gets edited).

Note that there seems to be some issue with the 'auto-cleanup' mechanism
removing no more valid override rules on file save, will check on that
next.

Related to T81059, found while investigating it.

Cleanup: SpaceGraph ED code: use boolean litterals when needed.

Fix (unreported) memory leak in Extrude mode of the Solidify modifier.

Fix LibOverride Resync generating orphaned data-blocks.

Part of the code handling deletion of old, not needed anymore local
override IDs, was not working properly, effectively only deleting one
ID ever.

New code should also be a bit faster, though this should not be really
visible from user perspective.

Related to T81059, found while investigating it.

Fix part of asserts in LibOverride when resynching.

We can only re-apply overrides fron the old local overrides to the newly
generated ones after all IDs have been properly remapped and renamed.

Otherwise override operations based on ID names may fail.

Related to T81059, found while investigating it.

LibOverride: Do not assert when failing to apply an override rule.

This is actually fairly common issue if lib data changes, just print out
an info message about it for now.

Fix crash related to liboverride differential operations code.

Root of the issue is how we generate the storage ID for the differential
override operations.

However, since those are disabled anyway currently, simply comment out
creation of this copy for now, we can revisit this if/when we decide to
re-activate differential overrides.

Related to T81059, found while investigating it.

Fix T80727: Drivers: deleting all keyframes leaves an uneditable f-curve.

A NULL bezier pointer does not mean that the fcurve is not editable, it
only is if it actually has some baked sample points too.

LibOverride: Tweak override creation code.

This is a first step towards supporting conversion of proxies, done
separately to make it easy to pinpoint in case it would create problems.

It is not expected to cause any change in behavior currently.

Fix (unreported) LibOverride: RNA asserts when applying overrides.

Some RNA setters require ID data they operate on to be in G_MAIN.
Unfortunately, when we apply overrides as part of a .blend file reading,
new Main is not yet made global one, so we have to do it temporarily
here.

This is a fairly ugly hack, but it should be harmless and safe.