add show_ignition parser

[ciesinsn]

Description

Addition of "show ignition" parser for IOSXE devices

Motivation and Context

Parser did not previously exist

Impact (If any)

None

Screenshots:

Checklist:

• [X] I have updated the changelog.
• [] I have updated the documentation (If applicable).
• [X] I have added tests to cover my changes (If applicable).
• [X] All new and existing tests passed.
• [X] All new code passed compilation.