[Nexthop] FBOSS Distro init service and default configs

[marif-nexthop]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

At boot, start a oneshot systemd service that launches a fboss_init.sh script to perform FBOSS distro initialization and setup e.g. copying right config files to /etc/coop etc.

• Added systemd service launches the script fboss_init.sh
  • The init script does the following steps for now
    • Copy /etc/coop configuration files based on the dmidecode output
    • Generate fruid.json file
• Added option to add default configs (qsfp_service and wedge_agent) for different platforms
• Added default configs for montblanc platform as an example

Test Plan

fboss_init systemd service

● fboss_init.service - FBOSS Initialization
     Active: active (exited) since Tue 2026-01-27 12:00:20 PST
     
Jan 27 16:05:34 fboss101 fboss_init[90731]: [fboss_init] Starting FBOSS initialization
Jan 27 16:05:34 fboss101 fboss_init[90732]: [fboss_init] Detected platform: minipack3
Jan 27 16:05:34 fboss101 fboss_init[90732]: [fboss_init] Using platform config directory: /opt/fboss/share/minipack3
Jan 27 16:05:34 fboss101 fboss_init[90731]: [fboss_init] Copied agent.conf: /opt/fboss/share/minipack3/agent.conf -> /etc/coop/agent.conf
Jan 27 16:05:34 fboss101 fboss_init[90731]: [fboss_init] Copied qsfp.conf: /opt/fboss/share/minipack3/qsfp.conf -> /etc/coop/qsfp.conf
Jan 27 16:05:35 fboss101 fboss_init[90731]: [fboss_init] Generated fruid.json: /var/facebook/fboss/fruid.json
Jan 27 16:05:35 fboss101 fboss_init[90731]: [fboss_init] FBOSS initialization complete

when system config files exist (skipped)

Jan 27 16:00:03 fboss101 fboss_init[90579]: [fboss_init] Starting FBOSS initialization
Jan 27 16:00:03 fboss101 fboss_init[90580]: [fboss_init] Detected platform: minipack3
Jan 27 16:00:03 fboss101 fboss_init[90580]: [fboss_init] Using platform config directory: /opt/fboss/share/minipack3
Jan 27 16:00:03 fboss101 fboss_init[90579]: [fboss_init] agent.conf already exists at /etc/coop/agent.conf (skipping)
Jan 27 16:00:03 fboss101 fboss_init[90579]: [fboss_init] qsfp.conf already exists at /etc/coop/qsfp.conf (skipping)
Jan 27 16:00:03 fboss101 fboss_init[90579]: [fboss_init] fruid.json already exists at /var/facebook/fboss/fruid.json (skipping)
Jan 27 16:00:03 fboss101 fboss_init[90579]: [fboss_init] FBOSS initialization complete