Instead of modifying the existing scf.for op, create a new op with memref OpOperands/OpResults and delete the old op.
New allocations / other memrefs can now be yielded from the loop. This functionality is deactivated by default and guarded against by AssertDestinationPassingStyle.
This change also introduces replaceOp, which will be utilized by all other bufferize implementations in future commits. Bufferization will then no longer rely on old (pre-bufferize) ops to DCE away. Instead old ops are deleted on the spot. This improves debuggability because there won't be any duplicate ops anymore (bufferized + not-yet-bufferized) when dumping IR during bufferization. It is also less fragile because unbufferized IR can no longer silently "hang around" due to an implementation bug.