lib: internal: nativeresolver: solution: refactored out 'CowMap'
lib: internal: nativeresolver: cowmap: divided set() into add() and remove()
lib: internal: nativeresolver: solution: use CowMap also for broken successors

This reduces the memory footprint of broken successors structures.
lib: internal: nativeresolver: optimization: avoided memory allocations while calculating best broken successor
Merge branch 'plus/nativeresolver-cowmap-for-broken-successors'