Closes #7663 (add routing for pre-indexed shapes)

As discussed early in #7663, there no way to provide routing information for pre-indexed shape in GeoShape filters and queries. This PR contains fixes for this issue:
Adds optional `routing` parameter to `indexed_shape` object in GeoShape builder/parser for filter and query.
Adds test for mandatory-routed pre-indexed GeoShape search.
Adds `routing` parameter description into geo_shape filter asciidoc.