Rationalize our presentation and handling of merged/alias symbols in the IDE.

Examples of where we could be better: 1. Quick info for an alias could present information about the alias, as well as information about what the alias points to. 2. Goto-type for a union type could allow you to go to any constituent union-type-element. 3. Goto-def on a merged symbol could allow you to go to any declaration. 4. Quick info on a merged symbol could show you all the constituent declaration pieces. etc. etc.