ASN.1 Test script doesn't catch missing types

The fix to v16.1.0 corrects a reference to a couple of undefined types ("ecgi" -> "ECGI"). But the ASN.1 versions previous to this pass the pipeline checks. I think this is because the script uses an ASN.1 parser i.e. it checks syntax but does not compile.

This is the kind of mistake we want to catch, but the current script doesn't. Getting an ASN.1 compiler to run in a GitLab runner presents may be a challenge.