Fix type confusion in nc_match_single()

This function assumes that if the "gen" is an OtherName, then the "base"
is a rfc822Name constraint. This assumption is not true in all cases.
If the end-entity certificate contains an OtherName SAN of any type besides
SmtpUtf8Mailbox and the CA certificate contains a name constraint of
OtherName (of any type), then "nc_email_eai" will be invoked, with the
OTHERNAME "base" being incorrectly interpreted as a ASN1_IA5STRING.

Reported by Corey Bonnell from Digicert.

CVE-2022-4203

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
