key to insert
value associated to the key to insert.
indicator if the value has been added, or the value associated with the key was already in the map
pointer to the element associated with the given key (either existing or new value).
Complexity: CPU: O(degree * log_degree(n)) Memory:O(log_degree(n))
Inserts the (key, value) in the tree. This is passing the copy of the value into the tree, so it's not necessary to manually create copy of it. Note that for the reference types, this will just copy the reference.