Rewrite GEOS reference implementation tests

[peterstace]

There are a few issues with the existing reference implementation tests:

• They were originally authored against a very old version of GEOS. This meant that a lot of exceptions were needed to be added. Now there are a lot of exceptions that are no longer needed.
• The checks are very messy compared to the rest of the database.
• Once we have a unified GEOS wrapper, the reference implementation checks should be much less confusing.