Move LoadAddrman from init to addrdb

Init should only concern itself with the initialization order, not the
detailed initialization logic of every module.

Also, inlining logic into a method that is ~800 lines of code, makes it
impossible to unit test on its own.

src/addrdb.h

@@ -10,12 +10,14 @@
 #include <net_types.h> // For banmap_t
 #include <univalue.h>
 
+#include <optional>
 #include <vector>
 
 class ArgsManager;
 class CAddrMan;
 class CAddress;
 class CDataStream;
+struct bilingual_str;
 
 bool DumpPeerAddresses(const ArgsManager& args, const CAddrMan& addr);
 bool ReadPeerAddresses(const ArgsManager& args, CAddrMan& addr);
@@ -46,6 +48,9 @@ public:
     bool Read(banmap_t& banSet);
 };
 
+/** Returns an error string on failure */
+std::optional<bilingual_str> LoadAddrman(const std::vector<bool>& asmap, const ArgsManager& args, std::unique_ptr<CAddrMan>& addrman);
+
 /**
  * Dump the anchor IP address database (anchors.dat)
  *