[Mosaic GPU] Fix layout inference for `tcgen05_mma` to be compatible with user-specified tile sizes.
Previously, we chose the largest possible swizzle value in order to determine
the tile size along the minormost dimension of the `tcgen05_mma`'s SMEM
operands.
While using the largest tiling possible is a reasonable thing to do, it is not
strictly necessary for correctness. As a result, it is possible for a user to
specify a smaller tiling, and still produce a valid program. In this case, our
strict assignment logic immediately made the system unsatisfiable, despite the
existence of a valid solution that would satisfy the user's constraints.
This change replaces the assignment with a new constraint `IsValidMmaTiling`.
This allows applying the user-specified constraint if it exists, and also
allows us to still conjure the largest possible tiling if none is specified.
PiperOrigin-RevId: 863444916