[C#] Add ToString() methods to Arrow classes

[asfimport]

We should add ToString methods to RecordBatch, Schema, Field, DataType, Table, and ChunkedArray.

The default implementation in C# is just to return the class name, which isn't very useful.

Reporter: Will Jones / @wjones127

_{Note: This issue was originally created as ARROW-15217. Please see the migration documentation for further details.}