Introduce `multipoint_array` interface; Refactors `point_distance` API to support multipoint to multipoint distance.

[isVoid]

Description

closes https://github.com/rapidsai/cuspatial/issues/704

Contributes to #703

This PR introduces Multipoint_array interface, and simplifies the API of point_distance. Also updates the point_distance to support multipoint-multipoint distance.

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [x] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.