Revert "SessionManager's getSessionStateTree() now returns an implementation of IWeaveTreeNode to work with WeaveTree.tsx."
Revert "SessionManager's getSessionStateTree() now returns an implementation of IWeaveTreeNode to work with WeaveTree.tsx."

This reverts commit c3e264f22246e36fda8d49d93df42d89881adcc9.

WeaveTeam/WeaveJS,WeaveTeam/WeaveJS,WeaveTeam/WeaveJS,WeaveTeam/WeaveJS