Add utility to extract strides from layout map in MemRefType.

The RFC for unifying Linalg and Affine compilation passes into an end-to-end flow discusses the notion of a strided MemRef (https://groups.google.com/a/tensorflow.org/forum/#!topic/mlir/MaL8m2nXuio).

This CL adds helper functions to extract strides from the layout map which in turn will allow converting between a strided form of the type and a layout map.

For now strides are only computed on a single affine map with a single result (i.e. the closed subset of linearization maps that are compatible with striding semantics). This restriction will be reevaluated / lifted in the future based on concrete use cases.

PiperOrigin-RevId: 270284686