Wrap multi-table output in `:wrap results` by default

[epost]

It seems like a good idea to wrap the output, especially in cases where it comprises multiple tables, in a results block like this:

#+begin_results

...

#+end_results

This makes it easy to collapse or expand all tables in one go, and ensures replacing existing results with newer ones will work correctly.

Although this can be done manually using header arguments, e.g. by specifying :wrap results (or even just :wrap) on the src block itself, it seems like a very desirable thing to do by default, from a UX standpoint.