* Make the methods of `CThreadInterrupt` virtual and store a pointer to
it in `CConnman`, thus making it possible to override with a mocked
instance.
* Initialize `CConnman::m_interrupt_net` from the constructor, making it
possible for callers to supply mocked version.
* Introduce `FuzzedThreadInterrupt` and `ConsumeThreadInterrupt()` and
use them in `src/test/fuzz/connman.cpp` and `src/test/fuzz/i2p.cpp`.
This improves the CPU utilization of the `connman` fuzz test.
As a nice side effect, the `std::shared_ptr` used for
`CConnman::m_interrupt_net` resolves the possible lifetime issues with
it (see the removed comment for that variable).
This change helps generalize shutdown code so an interrupt can be
provided to libbitcoinkernel callers. This may also be useful to
eventually de-globalize all of the shutdown code.
Co-authored-by: Russell Yanofsky <russ@yanofsky.org>
Co-authored-by: TheCharlatan <seb.kung@gmail.com>
