GridDevice serialization refactor (#6094)

* GridDevice serialization refactor.

* Fixed type and lint errors

* Fixed more mypy errors

* Addressed nits and small fixes

* Fix coverage checks; made from_device_information experimental

* Renamed _GateRepresentation fields to clarify purpose

* Updated _from_device_information() callsites

* Fix lint error

* Remove unnecessary _in_or_equals() check.

Gateset.gates is a collection of GateFamilies, so most branches in the check don't apply.