Reconsider tsconfig membership lookups for `.d.ts` files in `composite`

One thing that is surprising with 6.0 & 7.0 - if your `tsconfig.json` includes `.d.ts` file via `files`, `include`, or `types`, they will not be included due to changes to `rootDir` and `composite`. This can be surprising if the main project is not actually opened up. Maybe this doesn't make sense for `types`, but we may want to reconsider this.