Updates to issue management configuration.

[sjwaight]

This PR does the following:

• Remove the old probot-driven configs as they are no longer used.
• Merge in support for the changes from @chasewilson's PR for networking at cilium (Adds assignees to issues labeled networking and cilium #4571)
• Update GitOps config:
  • Split config out into three distinct files to manage - periodic parsing of issues; event-driven processing of issues; issue assignment to individuals/groups.
  • Descriptions for all items and comments in assignees file to help identify what configuration controls which flows.
  • Added:
    • Auto-assignment of issues marked as announcements to the announcing user if they have not assigned to anyone.
    • Stale configuration to align with expectations:
      • 14 days inactivity for unassigned issues that aren't bugs or feature requests
      • 30 days inactivity for unassigned bugs
      • 180 days inactivity for unassigned feature requests
      • 180 days inactivity for any announcements without activity

[microsoft-github-policy-service]

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