This was prompted by errors being returned that didn't "make any sense" to me, because it would for example return a "fee too low" error, when the "real" error was the child had something invalid, which disallowed CPFP evaluation. Rather than make judgment calls on what error is important(which is currently just return the "first"!), we simply return all errors and let the callers determine what's best.

Added a top level package_msg for quick eye-balling of general success of the package.

This PR also fixes a couple bugs:
 - Currently we don't actually broadcast a transaction, even if it was entered into our mempool, if a subsequent transaction causes PKG_TX failure.
 [... Other bugfix isn't relevant for our codebase]

ninja all check-all