Create self-contained Search asserts

[aprokop]

I opted for "duplicating" DTK_DBC instead of moving the original inside the search. This would allow us to modify ArborX exception at any time without having to spend time to fix any creeping DTK issues.

I also retained a single ASSERT call, and got rid of helper functions to maintain header-only flavor of the library.

[aprokop]

@dalg24 ready. I will address DTK_MARK_REGION in a separate PR that will introduce DTK_Search.hpp (a single header for the whole search library), as that would be the right place to put it in. Or not.

[codecov-io]

Codecov Report

Merging #543 into master will decrease coverage by 0.06%. The diff coverage is 85.96%.

@@            Coverage Diff             @@
##           master     #543      +/-   ##
==========================================
- Coverage    96.1%   96.04%   -0.07%     
==========================================
  Files         129      131       +2     
  Lines        9500     9528      +28     
==========================================
+ Hits         9130     9151      +21     
- Misses        370      377       +7

Impacted Files	Coverage Δ
...s/Meshfree/src/DTK_NearestNeighborOperator_def.hpp	100% <ø> (ø)	:arrow_up:
...earch/test/tstDetailsDistributedSearchTreeImpl.cpp	97.61% <ø> (ø)	:arrow_up:
...kages/Search/src/details/DTK_DetailsMortonCode.hpp	100% <ø> (ø)	:arrow_up:
packages/Search/test/tstDetailsBatchedQueries.cpp	95.83% <ø> (ø)	:arrow_up:
packages/Search/test/tstDetailsUtils.cpp	99.35% <ø> (ø)	:arrow_up:
...es/Search/src/details/DTK_DetailsTreeTraversal.hpp	97.19% <ø> (ø)	:arrow_up:
...ree/src/DTK_DetailsNearestNeighborOperatorImpl.hpp	100% <ø> (ø)	:arrow_up:
...ckages/Search/src/details/DTK_DetailsSortUtils.hpp	100% <ø> (ø)	:arrow_up:
packages/Search/test/tstLinearBVH.cpp	98.87% <ø> (ø)	:arrow_up:
...ages/Search/src/details/DTK_DetailsDistributor.hpp	100% <100%> (ø)	:arrow_up:
... and 11 more

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