9b52672700 For descriptor pubkey parse errors, include context information (Ben Woosley)
Pull request description:
This adds readily-available context information to the error string, for further disambiguation.
This is a revival of #16123 which was largely addressed in #16542.
Note 'Multi:' is used rather than 'multi():' as it also encompasses 'sortedmulti():'
ACKs for top commit:
achow101:
ACK 9b52672700
theStack:
ACK 9b52672700
Tree-SHA512: 96533ea8c3ac7010f9b62e75b4bd20b65aff843030eb91c7a88312975acecaaf17909b7d1841f45edc86dbf7fa402d208adb85f0673bd79b857dbebacb8c9395