Relax compare_tables to allow unexpected Indexes and Streams

[numberoverzero]

The comparison strictness is an artifact of the 1:1 model:table mapping.

Now multiple Models backed by the same table may have their own GSIs and LSIs. The correct check would assert that the expected Indexes are a subset of available Indexes, and do the usual validation on each of the expected Indexes.

For the new Stream work in #17, it's fine if the table has a stream that the model didn't expect. Again, another Model may use the stream but this one does not. This should only fail if the Model expects a Stream that doesn't exist, or the StreamViewType doesn't match.