To discover new exact deps, take into account only deps and constraints from the
new unit version (and not from every possible combination) as we probably
already looked at most of them.

This actually is an assymptotic improvement for _propagateExactTransDeps:
Accumalatively this routine doesn't take O(N^2*M) comparisons but rather O(N*M)
where N is the number of uvs picked and M is the number constraints.