Support filling a chunk/array subset into a target buffer

I.e. support https://docs.rs/zarrs/latest/zarrs/array/enum.ArrayBytesDecodeIntoTarget.html, seen in this API: [`Array.retrieve_array_subset_into`](https://docs.rs/zarrs/latest/zarrs/array/struct.Array.html#method.retrieve_array_subset_into)

Start by reading ArrayBytesDecodeIntoTarget and Array.retrieve_array_subset_into in the linked zarrs API documentation, then inspect zarrista's existing Python bindings for array retrieval. Done means the binding supports filling a chunk or array subset into a caller-provided target buffer, with behavior consistent with the referenced Rust API.

Written by the indexing model from the issue text.