Software renderer: Add a zfreeze related TODO.
VertexShaderManager: Remove a hardcoded projection hack.
VertexShaderGen: Remove Sonic Unleashed hack. Doesn't seem to be required anymore.

Either way, even if it's still needed for anything, this is not the correct way to fix the issue.
D3D/OGL: Add a TODO noting that we don't support GX_CULL_ALL, most notably required for accurate zfreeze emulation.