Harden response delivery to ensure services is consistent with server

Spoke with @andrewbranch

If you [add] a member to any protocol.*Response, there's a significant chance that your fourslash tests [will] work but it [won't] actually work over the TS Server because session.ts picked apart the response in the process of converting positions to line/character and didn't know to put it back

How could we fix it?

Destructuring with an object rest instead of requiring session.ts to name every property it wants to preserve