Introduce memref replacement/rewrite support: to replace an existing memref

with a new one (of a potentially different rank/shape) with an optional index
remapping.

- introduce Utils::replaceAllMemRefUsesWith
- use this for DMA double buffering

(This CL also adds a few temporary utilities / code that will be done away with
once:
1) abstract DMA op's are added
2) memref deferencing side-effect / trait is available on op's
3) b/117159533 is resolved (memref index computation slices).
PiperOrigin-RevId: 215831373