Fall back to real thread IDs when missing DetThreadId

[gatoWololo]

Our channels work send (Option, T) where T is the actual data and Option is a unique determininistic identifier for the data. We use an option as some threads may be spawned outside our spawn wrapper in some other crate (e.g. Rayon or Tokio spawns a thread). So these threads are assigned a DeThreadId of None. This means all information about the sender thread is lost. It would be useful for us to instead use a type like:

enum ThreadInfo {
  DetThreadId(DetThreadId),
  RealThreadId(RealThreadId),
}

In the case where threads are spawned outside our std::thread::spawn wrapper this would allow us to differentiate between:

• A real race: Which would look like two different ThreadInfo::ReadThreadId(id1) and ThreadInfo::ReadThreadId(id2)
• A non race: Messages coming all coming from the same ThreadInfo::ReadThreadId(id).

[gatoWololo]

We might want to take this one step further and consider any thread sending channel messages from an "initialized thread" (one without a DetThreadId) to be a bug. This would simplify the cases we have to handle and would keep our deterministic gurantee straightforward.