see https://basarat.gitbooks.io/typescript/content/docs/tips/nominalTyping.html and https://github.com/Microsoft/TypeScript/blob/7b48a182c05ea4dea81bab73ecbbe9e013a79e99/src/compiler/types.ts#L693-L698

fixes #7744

Without checking Capabilities

Add a new flag to the StoppedEvent that will trigger the debug adapter to be
queried for callstacks of the expanded threads in the callstack viewlet.