Blender Git Loki

Cleanup: Use span and float matrix type in direct boolean code

This commit includes a few simple improvements to the direct mesh
boolean code added recently.
- Passing the transforms and meshes to `direct_mesh_boolean` as spans
makes the function easier to call from C++.
- The definition of `TransMat`, was unecessary when we have the
`float4x4` type already used elsewhere in C++ code.

Differential Revision: https://developer.blender.org/D10592