Merge #11418: Add error string for CLEANSTACK script violation

Summary:
cee28fbc3 Add error string for CLEANSTACK script violation, preventing an "unknown error" if the CLEANSTACK error condition is set. (Mark Friedenbach)

Pull request description:

This prevents an unhelpful "unknown error" from being printed in test logs if the CLEANSTACK error condition is set.

Tree-SHA512: cd6764e930184aef3d662e40c67f2ea8aea8552a26d33a567d0315a19d707a82aa2afad9f48ecbb731aa5b77fbbfbd7a6a3a989fdb1424a1181350052ff2a9b5

Backport of Core PR11418

We had applied a similar fix to this previously, but this brings our error message inline with Core's (per feedback from https://github.com/Bitcoin-ABC/bitcoin-abc/issues/393)

Test Plan: ninja check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6697