Remove direct node->wallet calls in init.cpp

Route calls during node initialization and shutdown that would happen between a
node process and wallet processes through the serializable `Chain::Client`
interface, rather than `WalletInitInterface` which is now simpler and only
deals with early initialization and parameter interaction.

This commit mostly does not change behavior. The only change is that the
"Wallet disabled!" and "No wallet support compiled in!" messages are now logged
earlier during startup.

src/wallet/test/init_test_fixture.cpp

@@ -8,6 +8,8 @@
 
 InitWalletDirTestingSetup::InitWalletDirTestingSetup(const std::string& chainName): BasicTestingSetup(chainName)
 {
+    m_chain_client = MakeWalletClient(*m_chain, {});
+
     std::string sep;
     sep += fs::path::preferred_separator;