ENH: methods to return astropy Tables rather than VO specific tables

E.g. `Irsa.list_catalogs(full=True)`or `Irsa.query_sia()` currenlty returns a `DALResultsTable` as well as e.g. `Alma.query_tap` also returns a DALResultsTable.

I don't think this is useful for the astroquery users, and thus propose to add the `to_table()` or `to_qtable()` in the astroquery code and thus return astropy Table or QTable, out of the box.

What do you think @keflavich and @andamian

If the VO output is thought to be useful, then we can still provide access to it by an opt-in kwarg instead of returning it by default for everything.

Start by inspecting Irsa.list_catalogs(full=True), Irsa.query_sia(), and Alma.query_tap to identify their current return types and surrounding query code. Determine which methods should expose astropy Table or QTable by default and how VO-specific output remains available; done means the affected public methods consistently follow the agreed return policy.

Written by the indexing model from the issue text.