Replace session upload grace period with session tracker

[Joerger]

Changes:

• Update session_tracker expiration logic.
  • Once the SessionTracker.Expiry(), is reached, it will be removed from the backend.
  • If SessionTracker.Spec.Expires is set, it will be a strict expiration which won't be affected by the following dynamics.
    • This is used by kube sessions, which have a hard set expiration of 24 hours.
• Add SessionTrackerUpdateExpiry grpc request to enable dynamic updates of the session expiration based on session state.
  • In PENDING state, the session tracker will expire after 1 hour.
  • In 'RUNNING` state, if the session is active, the expiration will be extended every 10 minutes. As a result, the session will expire 1 hour after the session ends.
  • If the session is TERMINATED, then the expiration will be set to time.Now() to mark it for immediate removal.
• Update Upload completer to check for abandoned uploads by checking if the associated session has a non-expired tracker.
  • Replaces the grace period logic - Closes Session upload completer grace period bug #11348

[xacrimon]

Sorry, meant to post a suggestion diff comment but tripped up in the VSCode online UI and accidentally pushed a commit with the change, please have a look at the commit and see if it looks reasonable.