Refactor out translation.h

This is a prerequisite for introducing bilingual error messages.
Note: #includes are arranged by clang-format-diff.py script.

src/net.cpp

@@ -15,11 +15,12 @@
 #include <consensus/consensus.h>
 #include <crypto/common.h>
 #include <crypto/sha256.h>
-#include <primitives/transaction.h>
 #include <netbase.h>
+#include <primitives/transaction.h>
 #include <scheduler.h>
 #include <ui_interface.h>
 #include <util/strencodings.h>
+#include <util/translation.h>
 
 #ifdef WIN32
 #include <string.h>