[mlir][linalg][transform][python] Refactor TileOp mix-in.

This patch simplifies and improves the mix-in of the `TileOp`. In
particular:

* Accept all types of sizes (static, dynamic, scalable) in a single
  argument `sizes`.
* Use the existing convenience function to dispatch different types of
  sizes instead of repeating the implementation in the mix-in.
* Pass on `None` values as is of optional arguments to the init function
  of the super class.
* Reformat with default indentation width (4 spaces vs 2 spaces).
* Add a a test for providing scalable sizes.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D159417