Restore ability to have query params which are used by an index with a different name

It used to be possible to write an index that could make use of multiple query parameters, including ones with a name other than that of the index.

This feature was lost with the introduction of the catalog query plan, because Catalog.search now only applies indexes whose names are mentioned in the query.

This pull request restores the lost feature by giving indexes a way to declare additional names that they will make use of in the query, and by taking that info into account when determining the index query plan.

See collective/alm.solrindex#2 for an example of an add-on that was affected by this regression.