Introduce OptTimedelta

[Nayeraneru]

This PR addresses #20790 adding Msf::OptTimedelta as a reusable datastore option with built-in validation and normalization to seconds, so modules don’t need custom regex or manual conversions. It supports signed and compound durations (e.g. -5m, 1h30m, 2d). Kerberos-specific clock skew parsing has been removed, and all Kerberos consumers now use OptTimedelta directly, ensuring a single shared parsing path across the framework.

Note: I think lib/msf/core/exploit/remote/kerberos/clock_skew.rb is no longer need, can be deleted.

Verification

• Run Specs
  bundle exec rake db:create db:migrate db:seed RAILS_ENV=test
bundle exec rspec spec/lib/msf/core/opt_timedelta_spec.rb spec/lib/msf/core/exploit/remote/kerberos/client_spec.rb
• Start msfconsole
• Use a Kerberos-capable module, For example: use auxiliary/scanner/smb/smb_login
• set KrbClockSkew TIME, For example:

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