[mlir][linalg][bufferize] Handle scf::ForOp correctly in bufferizesToMemoryRead

From the perspective of analysis, scf::ForOp is treated as a black box. Basic block arguments do not alias with their respective OpOperands on the ForOp, so they do not participate in conflict analysis with ops defined outside of the loop.

However, bufferizesToMemoryRead and bufferizesToMemoryWrite on the scf::ForOp itself are used to determine how the scf::ForOp interacts with its surrounding ops.

Differential Revision: https://reviews.llvm.org/D111775