[v9_16] Add Oracle Linux 9
Backport of !6581 (merged)
This is a revival of now-nonexistent !6648 and the public version of now-closed isc-private/bind9!424.
In an attempt to help with moving this forward, I allowed myself to
rebase the original MR on top of the current version of v9_16
, which
turned out to be slightly tricky because of !6730 (merged).
I will leave it up to @marka & @mnowak to figure out whether all of those commits still need to be here.
Let's please get this merged before the October code freeze to minimize CI drift between branches.