Update/fix -pipeline-data-transfer; fix b/120770946

- fix replaceAllMemRefUsesWith call to replace only inside loop body.
- handle the case where DMA buffers are dynamic; extend doubleBuffer() method
  to handle dynamically shaped DMA buffers (pass the right operands to AllocOp)
- place alloc's for DMA buffers at the depth at which pipelining is being done
  (instead of at top-level)
- add more test cases

PiperOrigin-RevId: 224852231