Support Arrow C Stream interface containing stream of `Array`

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**

It is not currently possible to use arrow-rs's FFI to exchange something like an `ArrayStream` or `ChunkedArray` when those arrays do not represent RecordBatches. [`ffi_stream::ArrowArrayStreamReader`](https://docs.rs/arrow/latest/arrow/ffi_stream/struct.ArrowArrayStreamReader.html) will error if the data type of the stream is not `Struct`.

This makes it impossible in the general case to interop with a `pyarrow.ChunkedArray` or `polars.Series` (via Python).

The Arrow C Stream Interface _does_ support non-struct array types. `get_next()` of `ArrowArrayStream` returns an `ArrowArray`, and an `ArrowArray` can be any generic Arrow array. That Arrow array is _often_ a StructArray, with the understanding that the StructArray represents a RecordBatch, but it doesn't have to be.

Here:
https://github.com/apache/arrow-rs/blob/5508978a3c5c4eb65ef6410e097887a8adaba38a/arrow-array/src/ffi_stream.rs#L364-L367
you _assume_ that the data type of the stream is struct (and also assume that you can interpret the C Schema as a `Schema`), but that isn't required by the spec. To be more generic, you can [use the data type of the C Schema directly](https://github.com/kylebarron/arro3/blob/0829e34fe250314c2e068ff86e3c5e7ad003d607/pyo3-arrow/src/ffi/from_python/ffi_stream.rs#L89-L91).

**Describe the solution you'd like**

Some way to transfer a stream of `Array` via FFI.

**Describe alternatives you've considered**

There's currently no way to exchange a stream of generic arrays with arrow-rs, as far as I can tell.

**Additional context**

For full disclosure, I've already implemented this in my own library, pyo3-arrow. I have an [`ArrayReader`](https://docs.rs/pyo3-arrow/latest/pyo3_arrow/ffi/trait.ArrayReader.html) trait to parallel `arrow::RecordBatchReader`, and [vendored a derived copy of `ffi_stream.rs`](https://github.com/kylebarron/arro3/blob/0829e34fe250314c2e068ff86e3c5e7ad003d607/pyo3-arrow/src/ffi/from_python/ffi_stream.rs) to make it possible to handle this interop (while not necessarily materializing the entire stream as a `ChunkedArray`.

I'm currently fine with my vendored copy of FFI, but others may have the same issue.

Previous discussion in https://github.com/apache/arrow-rs/issues/5295#issuecomment-2402556354

Read arrow-array/src/ffi_stream.rs around lines 364-367, then compare the referenced pyo3-arrow ffi_stream.rs implementation. Trace ArrowArrayStreamReader's handling of the C Schema and determine how generic array types differ from Struct streams. Done means FFI can exchange non-Struct Array streams while preserving existing RecordBatch behavior.

Written by the indexing model from the issue text.