Slight Change to Merge by Distance Node

Current: Merge by distance node results in non-deterministic index numbers.

Proposed change: Add Bool input to node. This bool would be for the "use_index_order" of the function call "BLI_kdtree_3d_calc_duplicates_fast" inside Merge by Distance node.

This would allow those who need the result to keep the same index order to get the results they expect, and allow those who don't need it to have "faster results".

github.com/blender/blender/blob/a649ff7b983f181360bf86c81e8f85e7979a4db6/source/blender/geometry/intern/mesh_merge_by_distance.cc

This is a simple and quick change. I'd do it myself, but I always have issues using Github and Linux.

P.S. If there this causes a crash caused by accessing a index that's already been deleted, this can be fixed by setting Some Variable to "tree->nodes_len" then I to <Some Variable> in the loop, the inside the loop, subtracting the number of removed indexes from <Some Variable>.

github.com/blender/blender/blob/ae7c71ef09029a1fbadc0f4813ee233cdf2ee6b7/source/blender/blenlib/intern/kdtree_impl.h

Related: projects.blender.org/blender/blender/issues/107306