Blender Git Loki

Fix T92857: Deadlock in geometry nodes curve multi-threading

The spline code, especially Bezier splines, often make use of lazily
evaluation and caching. In order to do that, they use mutex locks.
When multi-threading, this can lead to problems. Further detail
can be found in rBfcc844f8fbd0d1.

To fix the deadlock, isolate the task before multi-threading
when holding a lock.

Differential Revision: https://developer.blender.org/D13229