Update GenieSession to support expiring sessions and encrypted cookies

[andreeco]

This PR modernizes GenieSession to match the newer session design:

• Extend Session with created_at and expires_at fields and a default TTL.
• Add rotate! to change the session ID and reset timestamps.
• Store the session ID cookie using encrypted=true.
• Keep the existing API (Session, session, set!, get, etc.) intact.

Tests were also added.

One also needs to update GenieSessionFileSession.jl.

Test Summary:  | Pass  Total  Time
Sessions Suite |   37     37  0.2s
Test Summary:  | Pass  Total  Time
session cookie |    5      5  0.0s