Fix race condition if several competing threads are inserting Metal
buffers into the MTLSafeFreeList simultaneously while a new list
chunk is being created.
Also raise the limit for an MTLSafeFreeListChunk size to optimize
for interactivity when releasing lots of memory simultaneously.
Authored by Apple: Michael Parkin-White
Pull Request: https://projects.blender.org/blender/blender/pulls/105254
7bdd82eca0