Fix bufferization of collapse_shape of subviews with size 1 dims.

Currently, there's an optimization that claims dimensions of size 1 are always
contiguous. This is not necessarily the case for subviews.

```
Input:

[
  [
    [0, 1],
    [2, 3]
  ],
  [
    [4, 5]
    [6, 7]
  ]
]

Subview:

  [
    [
      [0, 1],
    ],
    [
      [4, 5]
    ]
  ]
```

The old logic treats this subview as contiguous, when it is not.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D134026