[C++][Dataset] Consolidate similar tests for file formats

Between CSV/Parquet/IPC we have a number of very similar or in some cases essentially identical tests. As we're doing more refactoring and development it would be nice to consolidate these tests so that we can ensure all formats behave consistently and get the same level of testing. For instance, ARROW-11772 now adds more comprehensive tests for scanning IPC which don't yet apply to Parquet/CSV.

This sort of consolidation may also be nice to do in Python.