Extend BruteForce search to non-XYZ point types

[jeevan6996]

Summary

• add PointRepresentation support to BruteForce search
• keep the existing fast XYZ distance path when the representation is trivial 3D
• use full DefaultFeatureRepresentation dimensions for descriptor point types where available
• allow autoSelectMethod to fall back to BruteForce when FLANN/Nanoflann are unavailable
• add focused BruteForce tests for custom representations, FPFH descriptors, and sparse invalid descriptors

Fixes #6421.

Validation

• configured a focused local build with search/tests enabled
• built target: cmake --build /private/tmp/pcl-bruteforce-build-6 --target test_brute_force_search
• ran: ctest --test-dir /private/tmp/pcl-bruteforce-build-6/test -R brute_force_search --output-on-failure
• ran: git diff --check

[jeevan6996]

The CI linker failures were caused by AutoSelectMethod being explicitly instantiated for every PCL_POINT_TYPES, while BruteForce was precompiled only for the XYZ and descriptor subsets. That left symbols undefined for types such as SHOT352, Normal, and PointUV when the fallback was selected.

Updated search/src/brute_force.cpp to instantiate BruteForce for PCL_POINT_TYPES, keeping both instantiation sets aligned. Verified locally with Homebrew LLVM: pcl_search builds, test_brute_force_search links, and all 3 focused tests pass.

[mvieth]

Thanks for this pull request. Could you please explain why you did this condition, since none of the other search methods do it like this?

[jeevan6996]

Thanks. I checked the other search implementations and they default to DefaultPointRepresentation, which is limited to the first three float values unless a type-specific specialization exists.

This condition is intentional for BruteForce’s new non-XYZ descriptor support: types with descriptorSize need DefaultFeatureRepresentation so all descriptor dimensions are included in distance calculations. XYZ and ordinary point types retain the existing default behavior, and callers can still override the representation explicitly. Tests cover both descriptor and custom representations.