Improve Parallel Reading (CSV, JSON) / Help Wanted

### Is your feature request related to a problem or challenge?

As originally stated in #6922 (I'm not sure why the issue was closed) and discussed in #6801 the current `FileOpener` implementation for both, Csv and Json, are utilizing multiple GetRequests to adjust the byte range prior to parsing / reading the file itself.

This is suboptimal and can be improved - minimizing the latency due to multiple remote network requests.

### Describe the solution you'd like

I would like to reduce the number of GetRequests from 3 to 1.

This can be done by "overfetching" the original partition byte range; and then adjust the range by finding the newline delimiter similar to the solution already implemented.

The approach is outlined here: https://github.com/apache/arrow-datafusion/pull/6801#discussion_r1257465786 by @alamb

There are some edge-cases that need consideration, like "heterogenous object sizes" within a CSV row or JSON object, that leads to partition ranges overlapping on the same line, which can lead to reading the same line twice. Error handling/ retry when no newline can be found ("overfetching" range was to small) has to be handled, as well.

**POC**:
---
I already went ahead and implemented a POC which works and can handle some edge-cases like overlapping partition ranges; appropriate error handling / retry is still missing.

However, I definitely **need help** to improve upon this: https://github.com/marvinlanhenke/arrow-datafusion/blob/poc_optimize_get_req/datafusion/core/src/datasource/physical_plan/json.rs#L232-L381

The solution is inefficient due to line-by-line operations and buffer cloning / copying.
I tried different ways to handle the `GetResultPayload::Stream` by using BytesMut::new() & buffer.extend_from_slice; but I was not able to handle all the edge-cases correctly.

I'd greatly appreciate if someone can give some pointers; or take it from here to improve upon the POC.

### Describe alternatives you've considered

Leave as is.

### Additional context

None.

Start with datafusion/core/src/datasource/physical_plan/json.rs, especially the POC section linked in the issue, then read the approach discussed in pull request #6801. Trace FileOpener and GetResultPayload::Stream handling, and compare the CSV and JSON paths. Done means reducing the range reads from three GetRequests to one while handling overlapping ranges, missing newlines, retries, and avoiding the POC's inefficient copying.

Written by the indexing model from the issue text.