Merging the surface model into the master branch

The frames model (framework for accelerated modeling of embedded surfaces) is a GPU-friendly implementation of Geant-like hierarchical 3D solid modeling based on bounded half-spaces. The model can be constructed transparently on the host based on an in-memory VecGeom solid model and deployed to the GPU via simple API. frames provides header-only stateless navigation API on the GPU, similar to the interfaces used for navigating within the VecGeom solid model.

This is a beta implementation that provides feature-complete navigation for the majority of solid primitives supported by VecGeom, with (currently) comparable or better performance on the GPU.

The next steps after merging are:

• applying patches related to possible cmake options consolidation
• tagging a v2 pre-release on the master
• continuing to improve the surface model in parallel with the solid model in the master
• branching v2-cleanup (not now, but soon after the assessment) that will contain all non-backward compatible changes towards version 2, besides the improvements
  • basically, all improvements in master will need to be adopted by rebase/cherry-pick/copy also to the v2-cleanup branch
• organize spring cleanup sprint to initiate large part of the cleanup work
• replace the current solid model CUDA instrumentation with surface-based one, implementing also the portability layer
• consolidate and release version 2 in the fall