Safe join on Drop

[Roms1383]

This PR keeps spawned thread handle in StreamingSoundHandle to join it on Drop

StreamingSoundHandle size increases from 192 bytes to 216 bytes.
If this is of concern, I could gate it behind a feature gate.

While it's probably unnecessary in most contexts, I depend on kira in audioware which runs in a video game plugin context.

In this particular context, the game can reclaim plugin's resource anytime (e.g. when player kill game in Windows taskbar), which, at times, causes race condition leading to CTD like this:

This PR also bumps cpal to latest 0.17.3 as it's the continuity of the fix made there in PR 1098 for the very same reason, and available since 0.17.2.

[Roms1383]

Ok I tested it with the plugin in-game and it works great. Since the tests are passing, I think it's ready for review 😃

[Roms1383]

This being said I was reading other part of the code and noticed there's already a Drop implementation for StreamingSound. I'm gonna try simply updating cpal first as it seems my additional Drop implementation is probably unnecessary. I wished I noticed it before.

[Roms1383]

Sorry for the confusion, we also had a SDK update landing in the meantime which required changes on our side.
I'm gonna take some more time to do additional testing and possibly re-work this PR.
Thanks for your patience and understanding.

[Roms1383]

Ok, so the reasoning behind this PR is:

• no panic inside Drop for SendOnDrop<T>
• uses thread park with timeout instead of sleep to allow thread to wake spuriously
• no thread handle left unjoined on Drop
  • for StreamManagerController
    uses a Option<JoinHandle<()>> since there's a single instance of it (24 bytes)
  • for StreamingSound
    uses an AtomicPtr<JoinHandle<()>> (8 + 1 bytes) since there can be multiple instances, it keeps Shared size at 24 bytes (versus 16 previously)
• bump cpal to benefit from the same guarantee, as explained above