Fix non-deterministic redundancy check for space view spawning heuristic

[Wumpf]

What

• Fixes Unnecessary Camera space created in structure from motion scene #5258

The mechanism we used for determining whether a "recommended" space view is redundant was flawed in several ways, causing it to be order hash map order dependent among other things.

Small improvement to 3d space view heuristic that stop it from considering subspaces with ViewCoordinates.

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[Wumpf]

built this in pair programming together with @jleibs and reviewed it myself now again. Looking still good after a couple of days, so merging (;