[DirectX] initialize registers properties by calling addRegisterClass and computeRegisterProperties (#128818)

This fixes #126784 for the DirectX backend.
This bug was marked critical for DX so it is going to go in first. At
least one register class needs to be added via `addRegisterClass` for
`RegClassForVT` to be valid.
Further for costing information used by loop unroll and other
optimizations to be valid we need to call `computeRegisterProperties`.
This change does both of these.

The test cases confirm that we can fetch costing information off of
`getRegisterInfo` and that `DirectXTargetLowering` maps `i32` typed
registers to `DXILClassRegClass`.

0 files changed, 0 insertions, 0 deletions