[Codegen][CPU] Fold reshape-containing encoding relayouts to map_store. (#24533)

GPU's configuration pipeline folds the `pack`/`expand_shape`/`transpose`
relayout chain from encoding materialization into a single
`iree_linalg_ext.map_store` before tiling; CPU did not. For a non-row-
major encoding swizzle the intervening `tensor.expand_shape` (not a
`TilingInterface` op) blocks producer fusion and strands an untiled,
whole-tensor `pack` intermediate.

Mirror GPU on CPU:
- Add `RelayoutCombinationScope::DispatchReshape`: like `Dispatch` but
restricted to chains whose backward slice contains an
expand/collapse_shape. Pure pack/unpack/transpose chains tile fine and
are left alone.
- Run `CombineResultLayoutTransformation` with that scope in the CPU
configuration pipeline, after MaterializeDeviceEncoding.
- Skip `map_load`/`map_store` as `getRootOperation` candidates, so a
dispatch with a real compute op plus a `map_store` roots on the compute
op.

Inert for existing (row-major) CPU encodings.

Progress towards #24515.

Signed-off-by: Benoit Jacob <jacob.benoit.1@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>