[MLIR][XeGPU] Refactor layout propagation utilities (#179016)HEADmain

This PR refactors layout propagation into two distinct components:
result/anchor layout setup and source layout inference from the result.

For operations that require a specific result layout due to semantic or
hardware constraints, the propagation logic explicitly sets up the
result or anchor layout. Otherwise, it infers the source layout from the
backward-propagated consumer layout.

The result or anchor layout may differ from the backward-propagated
consumer layout; any such discrepancies are resolved via the existing
layout-conflict mechanism.

**This PR introduces the following utility functions:**

Source layout inference:

> inferBroadcastSourceLayout()
> inferMultiReductionSourceLayout()
> inferBitCastSourceLayout()
> inferShapeCastSourceLayout()
> inferInsertStridedSliceSourceLayout()

Result / anchor layout setup:

> setupMultiReductionResultLayout()
> setupBitCastResultLayout()
> setupInsertStridedSliceResultLayout()
> setupLoadMatrixAnchorLayout()
> setupStoreMatrixAnchorLayout()
> setupLoadGatherAnchorLayout()
> setupStoreScatterAnchorLayout()

Part of subgroup distribution related code changes are separated and
created as PR https://github.com/llvm/llvm-project/pull/179018/changes.

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