Add a function to access elements of a table that are intersecting a geometry

Implement the function get_reference_features_in_geometry() necessary for the entity initializer. This function gets the IDs if all geometries in a table which lie within a boundary by using intersections between the boundary and the smaller geometries, or the centroids of said geometries.

The function get_reference_features_in_geometry() currently on exposure-lib is primarily meant to work with tables within the sources schema when it comes to its usage on entity-initializer. The function is more appropriately placed here for an open use, and called within exposure-lib for specific exposure related usages.