[Python] Conventions around PyCapsule Interface and choosing Array/Stream export

### Describe the usage question you have. Please include as many useful details as possible.

👋 I've been excited about the PyCapsule interface, and have been implementing it in my [geoarrow-rust project](https://github.com/geoarrow/geoarrow-rs). Every function call accepts any Arrow PyCapsule interface object, no matter its producer. It's really amazing!

Fundamentally, my question is whether the existence of methods on an object should allow for an inference of its storage type. That is, should it be possible to observe whether a producer object is chunked or not based on whether it exports `__arrow_c_array__` or `__arrow_c_stream__`? I had been expecting yes, as pyarrow implements only the former on `Array` and `RecordBatch` and only the latter on `ChunkedArray` and `Table` (to my knowledge). But this question came up [here](https://github.com/shapely/shapely/pull/1953#discussion_r1529247534), where nanoarrow implements _both_ `__arrow_c_array__` and `__arrow_c_stream__`

I'd argue that it's simpler to only define a single type of export method on a class and allow the consumer to convert to a different representation if they need. This communicates more information about how the existing data is already stored in memory. But in general I think it's really useful if the community is able to agree on a convention here, which will inform whether consumers can expect this invariant to hold or not.

### Component(s)

Python