Merge in `bbq2`

[jamesmunns]

CC @ithinuel, @Sympatron, just making you aware that I've been prototyping a "next gen" version of bbqueue over in https://github.com/jamesmunns/bbq2, the idea was to iterate there, then someday merge it into this repo.

I don't think there is any action required, but I wanted it to share in case any of the nice things from over there could be useful over here.

[Sympatron]

Interesting. What kind of improvements did you make to bbq2?

[jamesmunns]

I did a talk about it here: https://sdr-podcast.com/episodes/bbqueue/

But the TL;DR is:

It uses generics to allow for multiple "flavors" of bbqueue, e.g. whether you have atomics or not, whether you want async or not, how you store the data (inline or externally, and in a static or in an arc).

It's the same core algorithm, but with more flexibility to reduce code duplication.