Migrate from OpenGL

Is your feature request related to a problem? Please describe.

OpenGL has been in deprecation since MacOS 10.9 and has been fully replaced by Metal 2 in 10.14. It can be removed at Apple's whims. Vulkan was essentially glNext so we should be moving ahead anyways.

Describe the solution you'd like

Options (in increasing order of likelihood):

1. Stop supporting OpenGL related functionality on MacOS (current status)
2. Use Metal instead. Official example of migration
3. Shift to Vulkan: This is a chance to take a look at how PCL handles OpenGL and potentially refactor it enabling better support for other backends.

If we shift to Vulkan instead, we can use libraries such a MoltenVK (Vulkan over Metal) to maintain one single code for all platforms. A lot of engines have reported that refactoring using Vulkan gives them significant speed-ups on the same hardware.

Describe alternatives you've considered

In the mean time, we can shift to GLOVE (GL over Vulkan) + MoltenVK to keep using current implementation in Mac.

The issue does not name files, tests, or entry points. Start by auditing PCL's OpenGL-related functionality and deciding whether the project should stop supporting OpenGL on macOS, migrate to Metal, or move to Vulkan with MoltenVK. Done means implementing and validating one selected migration path across the affected platforms.