Fix EntitiesNearPoint range query

Use a fixed range delta around the missile hit-location for neighboring entities to damage.
Use a common query for GAIA and non-GAIA entities.
Do not presume attackable entities have Health.
Fix an issue where gaia entities were returned twice.

This fixes concerns reported by elexis at rP23012 and by Freagarach at rP22754.

Differential Revision: https://code.wildfiregames.com/D2738