Remove the fancy RegisterSet class introduced in 4c2bff61e.

While it was some nice and fancy template usage, it ultimately had many practical issues regarding length of involved expressions under regular usage as well as common code completion tools not being able to handle the structures.
Instead, we now use a more conventional approach which is a lot more clean to use.
GSP: Fix a major regression introduced in ffda035c, due to which no display transfers were triggered at all anymore.
Pica/GPU: Change hardware registers to use physical addresses rather than virtual ones.

This cleans up the mess that address reading/writing had become and makes the code a *lot* more sensible.
This adds a physical<->virtual address converter to mem_map.h. For further accuracy, we will want to properly extend this to support a wider range of address regions. For now, this makes simply homebrew applications work in a good manner though.
Video core: Add utility class for vector operations.

I wrote most of this for ppsspp, so I hold full copyright over it.
In addition to the original release in ppsspp, this provides functionality to easily extend e.g. two-dimensional vectors to three-dimensional vectors.
Pica: Add float24 structure.

24-bit floating points are used internally for calculations on the GPU, however the current code will still emulate that with 32-bit floating points.
In the future we might want to accurately perform the calculations with correct bitness in the future, but for now we just wrap the calculations around this class.
Pica: Add command processor.
Pica: Add register definition for vertex loading and rendering.
Pica: Implement vertex loading.
Pica: Add vertex shader implementation.
Pica: Add primitive assembly stage.
Pica: Add triangle clipper.
Pica: Add basic rasterizer.