[Mosaic GPU] Implement canonicalization for `TiledLayout`s.
Layout canonicalization gets rid of unnecessary tiles and dimensions in
`Tiling`s---such that (1) any tiling operation partitions at least one
dimension into more than `1` tile, and (2) the leading dimensions of each tile are
not `1` (if canonicalizing a tile in this way leads to an empty tile, then the
tile is given shape `(1,)`---which is still a meaningful (final) tile).
Canonicalization allows simplifying the definition of a few of our predefined
layouts---`WGMMA`, `WGMMA_ROW`, `TCGEN05`, `TCGEN05_ROW`, and `TCGEN05_COL`.
PiperOrigin-RevId: 772933245
