Add support for "device-priority" type for templates variables

[fpluch]

Description

Add support for "device-priority" type for templates variables

Motivation and Context

Device priority type was missing from pango for template variables

How Has This Been Tested?

Tested with development panorama instance :

2023/03/28 14:59:40 XXX: Retrieving API key
2023/03/28 14:59:42 (op) show system info
2023/03/28 14:59:43 (op) getting plugin info
2023/03/28 14:59:43 Initialize ok
2023/03/28 14:59:43 (edit) template variable: $prio1
2023/03/28 14:59:43 Successfully created variable : {$prio1 device-priority 150}

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.

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