vkd3d-shader: Use 64 bit swizzles for 64 bit data types in VSIR.

The goal here is to be able to convert between SSA and TEMP easily, which will be the second preliminary pass for the CFG structurizer.

Ideally I would have added the check in commit 4/4 for TEMPs as well, but typing information from TPF sources is insufficient. This leaves the current validation inconsistent: we check that a register is always used either as a scalar or a vec4, but that "scalar" might be 32 bit in some cases and 64 bit in others. Maybe the right thing to do here is just give up on trying to put some typing on TEMPs and just say they're always 4x32 bit words. I don't know, I'll leave this for when the dust is more settled.