Blender Git Loki

Merge branch 'master' into temp-vert-normals-cleanup

Merge branch 'master' into temp-vert-normals-cleanup

Further changes and fixes to move normals out of MVert

Simplify normal node based on changes to normal storage

More progress moving vertex normals out of MVert

Merge branch 'master' into temp-vert-normals-cleanup

More changes and fixes to pass normals around separately from MVert

Initial changes to move normals out of MVert

Cleanup: Use C++ types and lambdas for mesh normal calculation

- Use `threading::parallel_for` for multithreading, for a simpler API,
more readable and concise code.
- Use `Span` and `Array` (only internally, the public API is still C)
for safer, more automatic memory management.
- Since code is much less verbose, combine the callbacks into the
main function. Note that the accumulation code could be more concise
with `float3`, I just wanted to keep these changes minimal.

Differential Revision: https://developer.blender.org/D12402