kernel: Pass interrupt reference to chainman

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>

src/test/validation_chainstatemanager_tests.cpp

@@ -393,7 +393,7 @@ struct SnapshotTestSetup : TestChain100Setup {
             // For robustness, ensure the old manager is destroyed before creating a
             // new one.
             m_node.chainman.reset();
-            m_node.chainman = std::make_unique<ChainstateManager>(chainman_opts, blockman_opts);
+            m_node.chainman = std::make_unique<ChainstateManager>(m_node.kernel->interrupt, chainman_opts, blockman_opts);
         }
         return *Assert(m_node.chainman);
     }