Template unit tests on search tree type
Created by: dalg24
The motivation for these changes is to be able to instantiate these same unit tests for the "brute force tree" as well. This PR provides the necessary changes to the helper functions to check results and construct trees.
You may notice I did not bother pushing the changes to all unit tests. I am still unsure on whether/how to split the file. Some of the tests (https://github.com/arborx/ArborX/blob/5935ea40b51dd66488f82027d72c1e2a55bf3ae8/test/tstLinearBVH.cpp#L333-L368 in particular) are specifically written for BVH
and would not make sense for the brute force tree. Also in my current working version I commented out https://github.com/arborx/ArborX/blob/5935ea40b51dd66488f82027d72c1e2a55bf3ae8/test/tstLinearBVH.cpp#L756-L763. Anyway my point here is I plan on cleaning these things out later.