Add Kerberos trace subscriber support

[davidgvad]

Summary

This PR adds an initial Kerberos trace foundation for shared Kerberos client flows.

It:

• adds a subscriber hook to Rex::Proto::Kerberos::Client
• adds KerberosSubscriber and KerberosLoggerSubscriber
• exposes KerberosTicketTrace and KerberosTicketTraceLevel through shared Kerberos auth option paths
• adds focused RSpec coverage for subscriber notifications, logger output, and serializer output

This is an initial Kerberos trace scaffolding PR, not the full CertificateTrace/KerberosTicketTrace project.

Verification

Run:

bundle _2.5.22_ exec rspec spec/lib/rex/proto/kerberos/client_spec.rb spec/lib/rex/proto/kerberos/client_subscriber_spec.rb spec/lib/rex/proto/kerberos/kerberos_logger_subscriber_spec.rb spec/lib/msf/base/serializer/readable_text_kerberos_trace_spec.rb

Expected:

• 16 examples, 0 failures

Run:

bundle _2.5.22_ exec msfconsole -qx "use auxiliary/gather/asrep; show advanced; exit"

Expected:

• KerberosTicketTrace appears under the Kerberos auth section
• KerberosTicketTraceLevel appears under the Kerberos auth section
• accepted values are summary, raw

Console Output

msfconsole showed:

• KerberosTicketTrace false
• KerberosTicketTraceLevel summary

under When LDAP::Auth is kerberos.

[github-actions]

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