Registering custom udf in datafusion-cli could be easier

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

It would be nice if we could essentially call `geodatafusion::register(...)`, and reuse
the basic datafusion-cli without a lot of copy/paste code or maintenance burden.

https://github.com/datafusion-contrib/geodatafusion/issues/84

### Describe the solution you'd like

I intend to post a PR where we export most of the current `main_inner` function, from the binary
into the `datafusion-cli` lib, that allows people customizing datafusion-cli with a default `CliSessionContext` to just call into the library for most of the configuration/argument parsing.

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

Start by reading the datafusion-cli binary's current main_inner function and the library API around CliSessionContext. Trace which argument parsing and configuration pieces can be exposed for custom registrations such as geodatafusion::register(...). Done means a custom CLI can reuse the default setup without copying the existing implementation.

Written by the indexing model from the issue text.