[Mosaic GPU][NFC] Add `SMEMTiling` layout.
This is sufficient to express all SMEM transforms that we infer, because:
- We support at most one tiling transformation.
- If we do have a tiling transformation, we will automatically add a swizzle with the max possible swizzle, so there's no need to have swizzle transforms as part of the equation system.
- We don't support any other transforms (e.g. transpose) at this level.
PiperOrigin-RevId: 810884001
