Logs don't show up in unit tests, and since this is debugging functionality (though not enabled for tests by default) it's better to do it this way.

DataReader is generally jank - it has a start and end pointer, but the end pointer is generally not used, and all of the vertex loaders mostly bypassed it anyways.

Wrapper code (the vertex loaer test, as well as Fifo.cpp and OpcodeDecoding.cpp) still uses it, as does the software vertex loader (which is not a subclass of VertexLoader). These can probably be eliminated later.

GetComponentSizes was unused, so we simplify this and get rid
of the branches.

Most of these became unneeded when fmt was introduced.