Remove confusing CAddrDB

The class only stores the file path, reading it from a global. Globals
are confusing and make testing harder.

The method reading from a stream does not even use any class members, so
putting it in a class is also confusing.

src/test/fuzz/data_stream.cpp

@@ -23,5 +23,5 @@ FUZZ_TARGET_INIT(data_stream_addr_man, initialize_data_stream_addr_man)
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
     CDataStream data_stream = ConsumeDataStream(fuzzed_data_provider);
     CAddrMan addr_man(/* asmap */ std::vector<bool>(), /* deterministic */ false, /* consistency_check_ratio */ 0);
-    CAddrDB::Read(addr_man, data_stream);
+    ReadFromStream(addr_man, data_stream);
 }