> Post core#18710, there isn't much left using boost::thread_group, so should just be able to replace it with the standard library. This also removes the last use of `boost::thread_interrupted`.
>
> After this change, last piece of Boost Thread we'd be using is `boost::shared_mutex`. See the commentary [[https://github.com/bitcoin/bitcoin/issues/16684#issuecomment-726214696|here]] as to why it may be non-trivial to swap that for `std::shared_mutex` in the near future.
This is a backport of core#21016