Add missing definitions in prep for scripted diff

The missing include and ArgsManager were found after applying the
scripted diff in the following commit.

src/bitcoin-tx.cpp

@@ -6,6 +6,7 @@
 #include <config/bitcoin-config.h>
 #endif
 
+#include <chainparamsbase.h>
 #include <clientversion.h>
 #include <coins.h>
 #include <common/args.h>

src/chainparams.cpp

@@ -5,6 +5,7 @@
 
 #include <chainparams.h>
 
+#include <chainparamsbase.h>
 #include <chainparamsseeds.h>
 #include <common/args.h>
 #include <consensus/merkle.h>

src/chainparams.h

@@ -22,6 +22,8 @@
 #include <unordered_map>
 #include <vector>
 
+class ArgsManager;
+
 /**
  * Creates and returns a std::unique_ptr<CChainParams> of the chosen chain.
  * @returns a CChainParams* of the chosen chain.

src/init.cpp

@@ -18,6 +18,7 @@
 #include <blockfilter.h>
 #include <chain.h>
 #include <chainparams.h>
+#include <chainparamsbase.h>
 #include <common/args.h>
 #include <consensus/amount.h>
 #include <deploymentstatus.h>