MB-16312 Preserve root node's metadata when tree height shrinks
MB-16312 Preserve root node's metadata when tree height shrinks

- If existing metadata is not copied into new root node after tree
height decreases, HB+trie can't fetch the child B+tree correctly.

wurikiji/forestdb,hisundar/forestdb,couchbase/forestdb,couchbase/forestdb,wurikiji/forestdb,hisundar/forestdb