fix: python schema repr does not truncate output

[danepitkin]

Fix #466

>>> import nanoarrow as na
>>> url = "https://github.com/apache/arrow-experiments/raw/main/data/arrow-commits/arrow-commits.arrows"
>>> schema = na.ArrayStream.from_url(url).schema
>>> schema
<Schema> non-nullable struct<commit: string, time: timestamp('us', 'UTC'), files: int32, merge: bool, message: string>

[jorisvandenbossche]

Looks good!

[paleolimbot]

Thanks!

I do think there's a point where printing out everything is more harmful than helpful (e.g., if there are thousands of columns); however, this is a substantial improvement over what is here now!

[danepitkin]

Thanks for the review! I suppose we could have a really high limit like 1000 chars in that case. Although, if a user prints out a schema, I assume they are in some sort of interactive or debug mode? In that use case, it might not make sense to limit the schema column output at all. 🤷