X509: Add "code sign" as purpose for verification of certificates

X509: Add "code sign" as purpose for verification of certificates

Code signing certificates have other properties as for example described in
CA Browser Forum documents. This leads to "unsupported certificate purpose" errors when
verifying signed objects.
This patch adds the purpose "codesign" to the table in X.509 certificate verification and
the verification parameter "code_sign" to X509_VERIFY_PARAM.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18567)