Improve online documentation page for DataFrame

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

It feels to me like the documentation page for DataFrame is a bit all over the place about what kinds of information it contains. It jumps around from common operations to using the Arrow C interface to rendering. I think this page could greatly benefit from some cleanup.

**Describe the solution you'd like**

Take a fresh look at the documentation site and come up with a better organization for the types of materials we are sharing. Make a better flow for new users approaching the project.

**Describe alternatives you've considered**

Status quo.

**Additional context**

We are probably going to add a new section describing how to access and use execution metrics https://github.com/apache/datafusion-python/pull/1381 , and it is not clear where this should be on the existing page. Hence, the need for a bit of overhaul.