Drop script_pub_key arg from createNewBlock

Providing a script for the coinbase transaction is only done in test code
and for CPU solo mining.

Production miners use the getblocktemplate RPC which omits the coinbase
transaction entirely from its block template, leaving it to external (pool)
software to construct it.

A coinbase script can still be passed via BlockCreateOptions instead.

A temporary overload is added so that the test can be modified in the
next commit.

src/node/types.h

@@ -3,8 +3,8 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 //! @file node/types.h is a home for public enum and struct type definitions
-//! that are used by internally by node code, but also used externally by wallet
-//! or GUI code.
+//! that are used by internally by node code, but also used externally by wallet,
+//! mining or GUI code.
 //!
 //! This file is intended to define only simple types that do not have external
 //! dependencies. More complicated types should be defined in dedicated header
@@ -14,6 +14,7 @@
 #define BITCOIN_NODE_TYPES_H
 
 #include <cstddef>
+#include <script/script.h>
 
 namespace node {
 enum class TransactionError {
@@ -43,6 +44,22 @@ struct BlockCreateOptions {
      * transaction outputs.
      */
     size_t coinbase_output_max_additional_sigops{400};
+    /**
+     * Script to put in the coinbase transaction. The default is an
+     * anyone-can-spend dummy.
+     *
+     * Should only be used for tests, when the default doesn't suffice.
+     *
+     * Note that higher level code like the getblocktemplate RPC may omit the
+     * coinbase transaction entirely. It's instead constructed by pool software
+     * using fields like coinbasevalue, coinbaseaux and default_witness_commitment.
+     * This software typically also controls the payout outputs, even for solo
+     * mining.
+     *
+     * The size and sigops are not checked against
+     * coinbase_max_additional_weight and coinbase_output_max_additional_sigops.
+     */
+    CScript coinbase_output_script{CScript() << OP_TRUE};
 };
 } // namespace node