b55555d rpc: Add testmempoolaccept (MarcoFalke)
Pull request description:
To check if a single raw transaction makes it into the current transaction pool, one had to call `sendrawtransaction`. However, on success, this adds the transaction to the mempool with no easy way to undo.
The call `testmempoolaccept` is introduced to provide a way to solely check the result without changing the mempool state.
Tree-SHA512: 5afd9311190135cee8fc1f229c7d39bf893f1028f29e28d34f70df820198ff97b4bf86b41cbbd6e6c36a5c30073cefa92d541c74a4939c7a2a6fa283dfd41b63
18815b4bfb