JcrSession.cachedNode should not use node.getChildReferences(cache).getChild(segment) for ChildReferences with UNKNOWN_SIZE

When looking up nodes using segments, JcrSession.cachedNode should test whether the parent node's ChildReferences size is UNKNOWN_SIZE. Looking up a child node of a parent with thousands of children could take a lot of time as the approach is to iterate over the children.

Recommendation for ChildReferences with UNKNOWN_SIZE is to locate nodes via WorkspaceCache.getChildReference(parenKey, nodeKey) instead.