Introduce anchor layout for XeGPU anchor ops: load_nd, store_nd,
prefetch_nd, dpas, load, store, prefetch, load_matrix, store_matrix, and
atomic_rmw. Anchor layout is permanent, and is guaranteed to be honored
by XeGPU distribution and lowerinngs once specified.
1. Add anchor_layout for XeGPU anchor OPs: load_nd, store_nd,
prefetch_nd, dpas, load, store, prefetch, load_matrix, store_matrix, and
atomic_rmw.
2. rename layout attributes to anchor_layout for these ops: load, store,
load_matrix, store_matrix
3. update layout propagation pass: Only when user doesn't specify anchor
layout, the pass computes a default layout and set to anchor op's
permant layout and use that for propagation. if user specified anchor
layout, the pass takes user-specified anchor layout. permant layout and
use that for propagation. if user specified anchor layout, the pass
takes user-specified anchor layout.
326a1a4bad