[SPARK-47041] PushDownUtils should support not only FileScanBuilder but any SupportsPushDownCatalystFilters

[faucct]

What changes were proposed in this pull request?

Making the usage more flexible by migrating it to a trait.

Why are the changes needed?

I want to implement a custom ScanBuilder supporting pushing predicates, but this code forces me to extend FileScanBuilder, though there is an interface exactly for that.

Does this PR introduce any user-facing change?

I guess, not.

How was this patch tested?

Was not tested.

Was this patch authored or co-authored using generative AI tooling?

No.