[mlir][linalg] Simplify the hoist padding tests.

Use primarily matvec instead of matmul to test hoist padding. Test the hoisting only starting from already padded IR. Use one-dimensional tiling only except for the tile_and_fuse test that exercises hoisting on a larger loop nest with fill and pad tensor operations in the backward slice.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D114608