Refactor how CowData manages its allocations

- Use an explicit type for the data prefix to enable easier changes.
- Explicitly store the capacity instead of using the next power of two.
- If resizing to a significantly larger size (more 2x the current
  capacity), assume that the caller has just resized to their final
  size and don't allocate any excess capacity.
- Trim the capacity less aggressively to fix edge cases when repeatedly
  adding and removing elements causing extreme performance issues.
- Do not rely on overflow checked operations to determine the maximum
  size, to avoid crashes with some compilers when using too large sizes.
- On 64-bit system increase the the maximum size to 0x7ffffff0,
  generally by a factor of the size of the elements.
- On 32-bit system the maximum size remains limited by the size of the
  address space / memory, but in some cases it may still be possible to
  allocate larger arrays compared to before.
- Add a minimum capacity to remove some unnecessary reallocation for
  small arrays.
- Remove a few unnecessary potential copies when resizing, adding or
  removing elements.