[mlir][Linalg] Introduce folding patterns to remove certain MemRefCastOp

Summary:
Canonicalization and folding patterns in StandardOps may interfere with the needs
of Linalg. This revision introduces specific foldings for dynamic memrefs that can
be proven to be static.

Very concretely:

Determines whether it is possible to fold it away in the parent Linalg op:

```mlir
  %1 = memref_cast %0 : memref<8x16xf32> to memref<?x?xf32>
  %2 = linalg.slice %1 ... : memref<?x?xf32> ...
  // or
  %1 = memref_cast %0 : memref<8x16xf32, affine_map<(i, j)->(16 * i + j)>>
         to memref<?x?xf32>
  linalg.generic(%1 ...) : memref<?x?xf32> ...
```

into

```mlir
  %2 = linalg.slice %0 ... : memref<8x16xf32> ...
  // or
  linalg.generic(%0 ... : memref<8x16xf32, affine_map<(i, j)->(16 * i + j)>>
```

Reviewers: ftynse, aartbik, jsetoain, tetuante, asaadaldien

Subscribers: mehdi_amini, rriddle, jpienaar, burmako, shauheen, antiagainst, arpith-jacob, mgester, lucyrfox, liufengdb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73565