fix(arrow/ipc): allow reading custom metadata from record batch message

[rkyleg]

I could not find a method to read the custom metadata out of the RecordBatch message, only the metadata from the schema, so I added an option to read custom metadata from record batch message in ipc reader. This was the api I came up with. I tried to follow the existing methodology of updating the current record batch in Read/Next. Let me know if any api changes should be made or if I am completely missing this functionality somewhere.

Rationale for this change

Allow reading custom metadata from record batch message similar to the iter_batches_with_custom_metadata function in the pyarrow library.

What changes are included in this PR?

Add an ipc.Option (WithCustomRecordBatchMetadata)
Add meta field in ipc.Reader struct to hold metadata
Check WithCustomRecordBatchMetadata option in next() method on Reader and, if true, read metadata from the

Are these changes tested?

Existing tests pass; however, I am not sure how to use the current test setup to test these changes because there isn't an api (that I can tell) to write this custom metadata to an ipc either. I will look into that next.
Also wasn't sure where to upload example arrow stream files.
I did create an example of using these changes here.
If you have any pointers here, I would be happy to write some tests.

Are there any user-facing changes?

No

[zeroshade]

@rkyleg Converting to draft — this PR doesn't yet meet our Pull Request quality criteria.

• ❌ Merge conflicts — this branch conflicts with main. See docs.

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