Python GIL release for PointCloud::OrientNormals*

Python GIL release for PointCloud::EstimateNormals and PointCloud::Vo…

…xelDownSample

Fix two crash bugs on Apple Silicon (isl-org#6008)

* Remove -nocompact_unwind and suppress warnings instead
* Fix crash bug on Apple Silicon on closing gui window (might be Ventura-only)

Add new Mitsuba Python example + update CPU rendering docs (isl-org#5991

)

* Add new material estimation example
* Update docs for CPU rendering for Ubuntu 22.04
Co-authored-by: Sameer Sheorey <[email protected]>

Build with libomp 11.1 and package it in the macOS wheel (isl-org#5679)

Fail build if newer libomp found
Install libomp 11.1.0 from old brew bottle for catalina (10.15)

make PaintUniformColor return by reference (isl-org#5566)

0.15.1 version bump (isl-org#4782)

0.15.0 version bump (isl-org#4778)

0.14.1 version bump (isl-org#4358)

v0.14.0 version bump (isl-org#4354)