Automatically test doc examples in user guide

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

While preparing for the 7.0.0 release, I manually stumbled on to the fact that the example on https://arrow.apache.org/datafusion/user-guide/example-usage.html (and linked in the main crate's readme) didn't work! see #1812

Describe the solution you'd like
I would like the examples in the user guide to be run as part of the normal CI in datafusion so that we have confidence they will work even if we do change the API

Describe alternatives you've considered
N/A

Additional context
@returnString had this working once upon a time using the doc-comments crate -- apache/arrow#9749 not sure what happened