to-do: investigate possibly unreachable LOC in `@std/streams/delimiter-stream`

We need to confirm whether the following LOC are indeed unreachable. If they are, with sufficient validation, they can be removed.
https://github.com/denoland/deno_std/blob/c52c6ee057cfd95ecc7a489dc1d0f99cc1d2e0c6/streams/delimiter_stream.ts#L199
https://github.com/denoland/deno_std/blob/c52c6ee057cfd95ecc7a489dc1d0f99cc1d2e0c6/streams/delimiter_stream.ts#L292

Start by reading streams/delimiter_stream.ts at the referenced lines 199 and 292, then trace the surrounding control flow and callers to determine whether those locations can execute. The work is done when reachability is validated sufficiently and the unreachable code is removed, if confirmed.

Written by the indexing model from the issue text.