Clean up pending escalations after moving incident to new project

What does this MR do and why?

This handles when an Incident Issue is moved to a new project.

• Removes any pending escalation records

A new escalation status is created on the new Issue (in the new project) by the existing process.

Screenshots or screen recordings

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How to set up and validate locally

1. Create an Incident Issue via GDK
2. Create an Escalation Policy + rules
3. Create the pending escalations like so:

incident = Issue.incident.last
policy = incident.project.incident_management_escalation_policies.first

# Create pending escalations
rules = policy.active_rules
rules.map do |rule|
  IncidentManagement::PendingEscalations::Issue.create!(
    target: incident,
    rule: rule,
    process_at: rule.elapsed_time_seconds.seconds.after(Time.current)
  )
end

1. Check that the pending escalations and escalation status exist

• incident.pending_escalations.count
• incident.incident_management_issuable_escalation_status

1. Move the isuse
2. Check that pending escalations are removed

• incident.pending_escalations.count

1. Ensure the newwly created incident has the escalation status

• Issue.incident.last.incident_management_issuable_escalation_status

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #330281 (closed)