Consolidate csv_opener.rs and json_opener.rs into a single example

[alamb]

Is your feature request related to a problem or challenge?

• Part of [EPIC] Improve examples to make them easier to navigate #11172

The large number of small examples in DataFusion leads to multiple problems:

• Makes it harder to find the relevant examples
• Unnecessarily large amounts of disk space on a full build (each example binary takes 100+ MB)
• Larger cargo t time (each binary must be linked / created)

Thus I think the fewer examples we have the

1. easier it will be to find the relevant examples
2. faster our dev experience will be

Describe the solution you'd like

csv_opener and json_opener examples demonstrate the same basic pattern for two different formats.

I would like to consolidate csv_opener.rs and json_opener.rs

• Consolidate the contents of
• https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/csv_opener.rs
• https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/json_opener.rs

Add an entry to the readme page:

• https://github.com/apache/datafusion/blob/main/datafusion-examples/README.md

Describe alternatives you've considered

No response

Additional context

I think this is a good first issue as the task is straightforward and doesn't require deep understanding of the DataFusion codebase

[cj-zhukov]

take