scripted-diff: Rename overloaded int GetArg to GetIntArg

Improve readability of code, simplify future scripted diff cleanup PRs, and be
more consistent with naming for GetBoolArg.

This will also be useful for replacing runtime settings type checking
with compile time checking.

-BEGIN VERIFY SCRIPT-
git grep -l GetArg | xargs sed -i 's/GetArg(\([^)]*\( [0-9]\+\|-1\|port\|BaseParams().RPCPort()\|Params().GetDefaultPort()\|_TIMEOUT\|Height\|_WORKQUEUE\|_THREADS\|_CONNECTIONS\|LIMIT\|SigOp\|Bytes\|_VERSION\|_AGE\|_CHECKS\|Checks() ? 1 : 0\|_BANTIME\|Cache\|BLOCKS\|LEVEL\|Weight\|Version\|BUFFER\|TARGET\|WEIGHT\|TXN\|TRANSACTIONS\|ADJUSTMENT\|i64\|Size\|nDefault\|_EXPIRY\|HEIGHT\|SIZE\|SNDHWM\|_TIME_MS\)\))/GetIntArg(\1)/g'
-END VERIFY SCRIPT-

Co-authored-by: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>

src/rpc/server.cpp

@@ -540,7 +540,7 @@ void RPCRunLater(const std::string& name, std::function<void()> func, int64_t nS
 int RPCSerializationFlags()
 {
     int flag = 0;
-    if (gArgs.GetArg("-rpcserialversion", DEFAULT_RPC_SERIALIZE_VERSION) == 0)
+    if (gArgs.GetIntArg("-rpcserialversion", DEFAULT_RPC_SERIALIZE_VERSION) == 0)
         flag |= SERIALIZE_TRANSACTION_NO_WITNESS;
     return flag;
 }