[mlir][linalg] Fix windows build issue in hoist padding.

Iterating backwardSlice and removing elements at the same time can fail on windows for specific build configurations (the code was introduced in https://reviews.llvm.org/D114420). This revision introduces a second vector to collect all operations and removes them after finishing the reverse iteration.

Reviewed By: hpmorgan

Differential Revision: https://reviews.llvm.org/D114775