[mlir][MemRef] Rewrite multi-buffering with proper composable abstractions

Rewrite and document multi-buffering properly:
1. Use IndexingUtils / StaticValueUtils instead of duplicating functionality
2. Properly plumb RewriterBase through.
3. Add support
4. Better debug messages.

This revision is otherwise almost NFC, if it weren't for the extra DeallocOp
support that would previoulsy make multi-buffering fail.

Depends on: D145036

Differential Revision: https://reviews.llvm.org/D145055