[R] Improved print methods for Arrow tabulars

[asfimport]

Right now, we return the schema, but it would be better if we returned the head of the tabular object so that people could see what they are interacting with.

We don't need to get a deterministic head here, just some idea of what's there.

Reporter: Jonathan Keane / @jonkeane

Related issues:

• [R] printing data in Table/RecordBatch print method (duplicates)

_{Note: This issue was originally created as ARROW-14697. Please see the migration documentation for further details.}