Backport upstream Ironic conductor graceful shutdown and drain functionality to downstream ironic-operator

Description:

Backport conductor graceful shutdown and task draining capabilities from upstream Ironic to the downstream version used in RHOSO 18. This enables truly non-disruptive conductor shutdowns and restarts by ensuring no in-progress actions are interrupted.

Acceptance Criteria:

• Review and identify all patches from upstream gerrit topics graceful and drain
• Backport
  • Graceful shutdown support that waits for all locks to be released before shutdown
  • Conductor drain functionality that prevents new tasks from being assigned to a conductor that is shutting down.

Technical Context:

• Upstream work completed in OpenStack Bobcat cycle
• Related gerrit topics: graceful and drain

References:

• Upstream gerrit topic: https://review.opendev.org/q/topic:%22graceful%22
• Upstream gerrit topic: https://review.opendev.org/q/topic:%22drain%22