[mlir][linalg] New tiling option: Scalarize dynamic dims

This tiling option scalarizes all dynamic dimensions, i.e., it tiles all dynamic dimensions by 1.

This option is useful for linalg ops with partly dynamic tensor dimensions. E.g., such ops can appear in the partial iteration after loop peeling. After scalarizing dynamic dims, those ops can be vectorized.

Differential Revision: https://reviews.llvm.org/D109268