Move autorunWithStore / derivedWithStore into autorun/derived + reader.store

[hediet]

Instead of

autorunWithStore((reader, store) => {
  const val = obs.read(reader);
  store.add(...)
});

We could make this work:

autorun(reader => {
  const val = obs.read(reader);
  reader.store.add(...)
});

The reader of autorun/derived would be of type

interface IReaderWithStore extends IReader {
   get store(): DisposableStore;
}

The implementation would only create the underlying disposable store on first access of store to avoid overhead in all the cases the store is not needed.