[C++] Expand test coverage for FieldPath and FieldRef Get/Find methods

[benibus]

Describe the enhancement requested

The FieldRef::Find* and FieldPath::Get functions provide many different overloads, however, many of these paths don't appear to be covered in arrow-type-test.

This is more of a concern for FieldPath::Get, which extracts child fields from arrays, chunked arrays, record batches, tables, etc. The underlying implementations aren't exactly trivial - nor are they equivalent. In addition, there's an (unwritten?) expectation that these functions are zero-copy so perhaps this should be tested explicitly.

In both cases, we could utilize test fixtures to do this in a uniform way.

Component(s)

C++