Move GetAllOutputTypes function from rpc/rawtransaction.cpp to rpc/util.{h|cpp}

src/rpc/util.h

@@ -39,6 +39,13 @@ class CPubKey;
 class CScript;
 struct Sections;
 
+/**
+ * Gets all existing output types formatted for RPC help sections.
+ *
+ * @return Comma separated string representing output type names.
+ */
+std::string GetAllOutputTypes();
+
 /** Wrapper for UniValue::VType, which includes typeAny:
  * Used to denote don't care type. */
 struct UniValueType {