[MLIR][XeGPU] Refactor Layout access interface  (#172125)

This PR builds on the anchor layout mechanism introduced in
https://github.com/llvm/llvm-project/pull/169267 and performs the
following refactoring:

1. Introduce getAnchorLayout() and setAnchorLayout() interface for
anchor ops to get and set layout attributes.

2. Add getLocalLayout() and setLocalLayout() utility functions, and
refactor workgroup/subgroup distribution patterns to use these APIs.
These utilities access the layout information directly and locally,
without relying on global propagation.

3. Introduce localPropagateLayoutsFromAnchor(), a utility used by
subgroup distribution to unify non-anchor layout setup.
This function is intended to be invoked upfront by all layout-based
passes (including workgroup/subgroup distribution and unrolling) to
propagate layouts from anchor ops to non-anchor ops.
After this step, patterns within the pass should exclusively use
getLocalLayout() / setLocalLayout().

4. Refactor getDistributeLayoutAttr() and setDistributeLayoutAttr() to
remove special-case handling. These APIs now operate in a uniform order:
anchor ops first, then non-anchor ops, and finally block arguments.
These APIs will be deprecated on long run. 

5. Refactor patterns in wg/sg distribution, load optimization passes to
use get/setAnchorLayout() and get/setLocalLayout().

6. Update test cases to enforce that anchor ops must use—and only
use—anchor layouts.