This commit adds multiple test cases to the X.509 CRT parsing test suite
exercising the stack's behaviour when facing CertificatePolicy extensions
that are malformed for a variety of reasons. It follows the same scheme
as in other negative parsing tests: For each ASN.1 component, have test
cases for (a) unexpected tag, (b) missing length, (c) invalid length
encoding, (d) length out of bounds.
6dfa665398