[build] Move rpc utility methods to rpc/util

Moves the following utility methods to rpc/util and moves that unit to
libbitcoin_common so they can be accessed by all libraries.

- `RPCTypeCheck`
- `RPCTypeCheckArgument`
- `RPCTypeCheckObj`
- `AmountFromValue`
- `ParseHashV``ParseHashO`
- `ParseHexV`
- `ParseHexO`
- `HelpExampleCli`
- `HelpExampleRpc`

src/test/script_tests.cpp

@@ -13,7 +13,7 @@
 #include <util/system.h>
 #include <util/strencodings.h>
 #include <test/test_bitcoin.h>
-#include <rpc/server.h>
+#include <rpc/util.h>
 
 #if defined(HAVE_CONSENSUS_LIB)
 #include <script/bitcoinconsensus.h>