test: improve test-abort-uncaught-exception

Add `SIGTRAP` to allowed signals (seen on PPC machines in CI).

Improve message when assertion fails in test-abort-uncaught-exception by
providing the signal name that was not expected.

PR-URL: https://github.com/nodejs/node/pull/14013


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>