CI: Save more sanitizer-undefined artifacts on failure

Note: !1782 (merged) depends on this MR (it has it merged-in already).

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Summary

The sanitizer-undefined CI job was not saving all of the logs on failure. This CI job is optional and may fail, but it's still useful to see all of the bitcoind logs and other things when trying to troubleshoot spurious or not-so-spurious failures.

This MR adds such a facility.

Test Plan

Verify that the artifacts.zip for the sanitizer-undefined CI job contains more stuff such as the build/tmp directory on failure. This may require restarting the job a few times until it randomly fails (which it does maybe 1/5th of the time).