[Parquet Metadata Cache] Add an API to review the contents of the Cache #17091

Is your feature request related to a problem or challenge?

• part of [Epic] Enable parquet metadata cache by default #17000

We are adding a parquet metadata cache to ListingTable 🎉 (thanks @nuno-faria @jonathanc-n and @shehabgamin )

It turns out it is somewhat tricky to get right, and it is not always clear what is going on. Especially tricky is when the metadata is cached with page indexes, and sometimes without it, for example see this PR:

• feat: Use Cached Metadata for ListingTable Statistics #17022

Describe the solution you'd like

I would like some way to see the contents of the cache with basic statistics

Describe alternatives you've considered

I suggest a twofold approach:

1. Add APIs to the DefaultFileMetadataCache itself
2. Add a function in datafusion-cli that uses those APIs to show the cache state

This two pronged approach would

1. Help debug the working of the cache with datafusion-cli
2. Ensure the APIs on the cache can be used to build useful introspection tools
3. Offer an example of how to build such a thing for others

An example might look like

select * from parquet_metadata_cache()

And the output might look ike

I think we could model its implementation on the parquet_metadata function: https://datafusion.apache.org/user-guide/cli/usage.html#parquet-metadata

Additional context

No response