Adopt a similar strategy to proj for geo-types compatibility

Although polyline also uses LineStrings, these can be primitively represented without too much trouble. Should we thus adopt a similar strategy to the proj crate, enabling geo-types compatibility by default but allowing a more simple option for consumers who don't want or need the overhead?

Start by examining the current polyline representation and the proj crate's compatibility strategy, then review how geo-types represents LineStrings. Determine the design for enabling geo-types compatibility by default while offering a simpler option without its overhead. Done means the compatibility behavior and opt-out path are agreed, implemented, and covered by appropriate tests.

Written by the indexing model from the issue text.