feat(panos-upgrade-assurance): upgrade assurance modules introduction

[FoSix]

this is a cleaner version of #437
all suggestions from that PR were taken into consideration

Description

Introducing Ansible modules that wrap the PanOS Upgrade Assurance package.

Motivation and Context

The PanOS Upgrade Assurance package is just a set of libs that have to be wrapped with some code. One way of doing this are Ansible modules. This PR introduces 4 modules:

• panos_readiness_checks - runs readiness checks on a device
• panos_state_snapshot - take a snapshot of a device's state
• panos_snapshot_report - produces a report from a comparison of two snapshot in a form of a dictionary
• panos_active_in_ha - a helper module to quickly verify if a given node in an HA pair is active or passive.

Since the package itself is based on pan-os-python, these modules follow the provider block standard used widely in this collection.

How Has This Been Tested?

Already used on production as local modules.

Screenshots (if appropriate)

Types of changes

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

Checklist

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