Enabled ``--page-size`` as global argument.

The page size controls the amount of items returned by
each page while paginating. Smoke tests were added for ``ec2``
and ``s3api`` to ensure the parameter does what is expected to
do for known paginating operations.

cc @jamesls @danielgtaylor
Some of the unit test failed via a key error when I did not use ``getattr()``.  I am going to change it and see if the unit tests need to be updated or something else.