hard cloning should check `offset === 0`

[kylebarron]

I.e. in this example if you look at

table.getChildAt(0)

you'll see

Vector [IntVector<Int>] {
  _offsets: Uint32Array(4) [ 0, 1, 2, 3 ],
  data: [
    Data {
      type: [Int32 [Int]],
      children: [],
      dictionary: undefined,
      offset: 0,
      length: 1,
      _nullCount: 0,
      stride: 1,
      values: [Int32Array],
      nullBitmap: Uint8Array(0) []
    },
    Data {
      type: [Int32 [Int]],
      children: [],
      dictionary: undefined,
      offset: 1,
      length: 1,
      _nullCount: 0,
      stride: 1,
      values: [Int32Array],
      nullBitmap: Uint8Array(0) []
    },
    Data {
      type: [Int32 [Int]],
      children: [],
      dictionary: undefined,
      offset: 0,
      length: 1,
      _nullCount: 0,
      stride: 1,
      values: [Int32Array],
      nullBitmap: Uint8Array(0) []
    }
  ],
  type: Int32 [Int] { isSigned: true, bitWidth: 32 },
  stride: 1,
  numChildren: 0,
  length: 3
}

So the second Data is a zero copy slice on the input. This means that if you checked if it's shared, it would say it's not shared because the view occupies the whole buffer? Need to double check this.

In any case, implementing hard cloning with slicing shouldn't be too hard, copying from the arrowjs method that has subarrays