[feature] Update project search fields on user full name change

**Purpose**
Originally, if a user changes his name and searches for his public projects, his public projects would be under his previous name, instead of the latest one.

**Cause**
Changing and saving the full name does not trigger a update on search on his projects, so the search fields that yield to the project remains unchanged.

**Changes**
Call <code>self.update_search_nodes()</code> to call <code>update_search()</code> on each node a user is a contributor on.

**Side effects**
Quote from Brian G: "Be careful on this. If Johanna or Brian N change their name, that means you would have to update a bunch of things. We were thinking that we would want to make this a long-running task rather than something that happens immediately, otherwise it might severely impact the OSF's performance."