chore: various async fixes

[vados-cosmonic]

Stuff that I ran into as I was going through:

• fetch -> from-stream
• spacing changes
• clarity around referenced WAT in separate sections

I think the call stack example needs to be made more approachable, but I don't know how to make it clearer -- I just wasn't able to wrap my mind around which parts were the component versus the host.

The concept that component-incoming async calls are Tasks and component-outgoing async calls are SubTasks which pair with a Task on the other side make sense. The additional wrinkle that when hosts call into components there is only a Task makes sense, but I couldn't make sense out of the following...

[Host caller] <- [Task] <- [Subtask+Task]* <- [Subtask] <- [Host callee]

I didn't put it in the PR but would like opinions on the following:

    [Host]
        ↓ calls component (host->component)
[Component Task]
        ↓ calls component (component -> component)
[Component Subtask <> Component Task]*
        ↓ calls host (component -> host)
 [Component Subtask]
        ↓ receives component call
[Host callee]

[lukewagner]

I'm not sure this sentence is an improvement.

[vados-cosmonic]

yeah, I can revert this -- I wasn't sure the "at any time" was necessary but it's hard to restate this, and I think the phrase "cal stack" was used too many times.

Maybe will be a callstack of the general form makes sense.

[vados-cosmonic]

OK I've updated it, WDYT?

[lukewagner]

I didn't put it in the PR but would like opinions on the following:

Good start, and I like the vertical format with annotations on the arrows. Riffing on it a bit, wdyt:

[Host]
  ↓ host calls component export
[Component Task]
  ↓ component calls import implemented by another component's export 0..N times
[Component Subtask <> Component Task]*
  ↓ component calls import implemented by the host
[Component Subtask <> Host task]

[lukewagner]

Beautiful, thanks. One suggestion:

[vados-cosmonic]

Thanks again for the close review @lukewagner !