[mlir][linalg] Pad independent of application order (NFC).

This revision makes the padding pattern independent of the application order. It addresses the concern that we cannot rely on the execution order of the greedy rewriter (https://reviews.llvm.org/D114689). Instead, the pattern is updated to apply repeatedly till all operations are padded.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D114851