Blender Git Loki

Fix T86654: wrong Vertex Interpolation option default when importing alembic caches

This resulted in bad motion blur from alembic animation when imported
after rB83980506957c (because it was now OFF by default).
When imported in a version prior to rB83980506957c and saved, this was
still working fine.

Vertex interpolation option introduced in rBbab2260b59c7 was defaulting
to ON (correct) in that commit, but was lost in rB83980506957c.

Now switch this to ON by default again.

Note: if you have a file that was (incorrectly) imported with a version
after rB83980506957c you'll have to enable Vertex Interpolation option
on every MeshSequenceCache modifier by hand.

Maniphest Tasks: T86654

Differential Revision: https://developer.blender.org/D10876