Amos Jeffries

@kinkie, this is failing Jenkins due to lack of pandoc build dependency. Can that be fixed soonish?

Bionic passed its EOL April 2023. Can we remove it from v7 testing?

> > I have intentionally avoided creating Async namespace, this PR touches so much code already. > > FWIW, I do not think creating Async namespace is a good idea...

@kinkie, also be aware the `AsyncEngine` is an interface for the `Engine` mechanism, not the part of `AsyncJob` mechanism.

Updated commit description to clarify latest change and pass Anubis requirements. Testing details dropped: ``` Requirements (test environment): FreeBSD kernel with KERN_TLS enabled OpenSSL built with KTLS enabled % kldload...

@rousskov, please re-review latest code after my changes.