Fix T81168: 2.8x Crash when loading 2.79 file.

Object in the 2.7x file is on no layer at all, while this is not really
expected nor considered valid, better to cope with the case gracefully
than crash.

To be backported to 2.90 and 2.83.

LibOverride: Tweak messages when some sub-item is not found when applying overrides.

Fix T78343: Most properties of Ocean modifier should not be animatable.

Properties that are only used when initializing the simulation cannot be
animated (the changes in their value would not be taken into account).

LibOverride: Better handling of cleanup of 'insert' operations in collections.

Before, it might have been possible in some cases (when there were no
items at all anymore in the collection) to miss that cleanup step,
leaving ghost useless and invalid operations around.

LibOverride: Cleanup: reserve debug messages to debug builds.

LibOverride: Tweak messages when some sub-item is not found when applying overrides.

LibOverride: Fix some cleanup of unused override operations.

Handling of pointer replacements in collection items lead to validating
all operations for a given property, when some might actually be no more
valid and would need to be cleaned up.

Related to T81059, found while investigating it.

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.