Checkpoint Harmony Endpoint - Updated logo and dashboard as per guideline (DataDog#21287)

* updated logo and dashboard as per guideline

* Update checkpoint_harmony_endpoint/assets/dashboards/checkpoint_harmony_endpoint_overview.json

* Fix image and add dark mode version

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Co-authored-by: dkirov-dd <166512750+dkirov-dd@users.noreply.github.com>
Co-authored-by: Enrico Donnici <enrico.donnici@datadoghq.com>
Co-authored-by: David Kirov <david.kirov@datadoghq.com>

Author: 3 people