feat: mach-o certificate parsing implemented with der_parser

[latonis]

As discussed in #235, implementing the certificate parsing with der_parser to reduce dependencies and potential headaches.

Depends on #275, as the ASN.1 parsing functions were specific to PE before this PR.

[latonis]

Open to discussing how much CMS data we return.

Currently we expose the following:

Certificate {
      issuer: c.x509.issuer.to_string(),
      subject: c.x509.subject.to_string(),
      is_self_signed: c.x509.issuer
          == c.x509.subject,
  }

[plusvic]

Open to discussing how much CMS data we return.

Currently we expose the following:

Certificate {
      issuer: c.x509.issuer.to_string(),
      subject: c.x509.subject.to_string(),
      is_self_signed: c.x509.issuer
          == c.x509.subject,
  }

I would like to expose as much data as in the pe module if possible. This is the structure that we are currently exposing in the pe module:

message Certificate {
  optional string issuer = 1;
  optional string subject = 2;
  optional string thumbprint = 3;
  optional int64 version = 4;
  optional string algorithm = 5;
  optional string algorithm_oid = 6;
  optional string serial = 7;
  optional int64 not_before = 8 [(yaml.field).fmt = "t"];
  optional int64 not_after = 9 [(yaml.field).fmt = "t"];
}

I guess this information is also available for Mach-O certificates, right? I would also add the is_self_signed field to the PE module.