This and the following commit seek to decouple the libbitcoinkernel
library from the shutdown code. As a library, it should it should have
its own flexible interrupt infrastructure without relying on node-wide
globals.
The commit takes the first step towards this goal by de-globalising
`ShutdownRequested` calls in kernel code.
Co-authored-by: Russell Yanofsky <russ@yanofsky.org>
Co-authored-by: TheCharlatan <seb.kung@gmail.com>
This is a partial backport of core#27861
https://github.com/bitcoin/bitcoin/pull/27861/commits/edb55e2777063dfeba0a52bbd0b92af8b4688501
Depends on D18965