Add Validations after Failover for HA Upgrades

[GrantGabbert]

Description

Added changes to perform validations after the initial failover. This adds an additional readiness check as well as snapshot (with comparison). To support this, added the following:

• New sub-playbook, "PAN-OS Network Operations - Upgrade Assurance - HA Test" that runs the readiness check, snapshot, and validation
• Added validation task to "PAN-OS Network Operations - Device Upgrade Loop" playbook
• Added incident fields to store/display HA validation results:
  • HA Assurance Test Result
  • HA Comparison Test Raw
  • HA Readiness Check Result
  • HA Readiness Test Result
  • HA Snapshot Comparison Result
  • HA Snapshot ID
  • HA Snapshot
  • HA Upgrade Assurance report
  • Snapshot Check List
• Add the "Snapshot Check List" incident field to the "pan-os-assurance-run-snapshot" tasks in playbooks
  • PAN-OS Network Operations - Upgrade Assurance - Assurance Test
  • PAN-OS Network Operations - Upgrade Assurance - First Snapshot
• Updated "PAN-OS Network Operations - Device Upgrade" layout to display new incident fields

Motivation and Context

To handle cases where there is a catastrophic bug in the new code version, validations should be performed after the failover, but before beginning the upgrade on the new passive. This resolves #22

How Has This Been Tested?

Tested by running upgrades on HA pairs using 440 firewalls.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist

• [X] I have updated the documentation accordingly.
• [X] I have read the CONTRIBUTING document.
• [X] I have added tests to cover my changes if appropriate.
• [ ] All new and existing tests passed.