Many of the fancy `ArrayHandle`s are read-only and therefore connot
really create write portals. Likewise, many `ArrayHandle`s (both read-
only and read/write) have no way to resize themselves. In this case,
implementing the `CreateWritePortal` and `ResizeBuffers` methods in the
`Storage` class was troublesome. Mostly they just threw an exception,
but they also sometimes had to deal with cases where the behavior was
allowed.
To simplify code for developers, this introduces a pair of macros:
`VTKM_STORAGE_NO_RESIZE` and `VTKM_STORAGE_NO_WRITE_PORTAL`. These can
be declared in a `Storage` implementation when the storage has no viable
way to resize itself and create a write portal, respectively.
Having boilerplate code for these methods also helps work around
expected behavior for `ResizeBuffers`. `ResizeBuffers` should silently
work when resizing to the same size. Also `ResizeBuffers` should behave
well when resizing to 0 as that is what `ReleaseResources` does.
