BUG: column order should have no effect

While I was fixing https://github.com/astropy/pyvo/pull/445 I noticed that the code picked the first column that matched the criteria (e.g. it did matter where I added the extra info in the test data).
However, the column order should have no effect, e.g. we should parse all and raise an exception if there are multiple columns matching or have a better hierarchy for what to look for.

I'm opening this issue to make sure we double check all service types for this type of hidden regression/assumption.

Start by reviewing PR 445 and the service-type parsing paths it changed, then identify the tests and test data covering column matching. Check each service type for assumptions about column order and add reordered-column cases; done means matching behavior no longer depends on order and ambiguous matches follow an agreed rule.

Written by the indexing model from the issue text.