[gNOI Reboot] Initial changes to bring framework container to SONiC

[kishanps]

Why I did it

Add framework container code to handle gNOI reboot.

How I did it

The framework container does the following at a high level

• Run a reboot backend process that listens on redis channel for reboot notifications (sent by gNOI frontend)
• Validate the reboot process and send the request over dbus to sonic-host-services
• Respond to redis channel notificaitons for reboot status

How to verify it

Unit tests included in the PR.

Description for the changelog

Add framework container bringup code for gNOI reboot support.