[HONEYCOMB-171] Optimize subtree handler creation

[vvalderrv]

If there is a subtree handler A, handling also B and C nodes, check if there is not a dedicated writer for C. Because if there is, the subtree writer can be recreated/optimized to handle only unhandled nodes (in this case B).

This would enable handler overriding in cases where default implementation handles nodes in a single subtree handler without having to reduce the scope of subtree handler in its registration code.