[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

PR commit stack:

1. [Nexthop][m4340nhp] Add the platform_manager config #1871
2. This (top of stack)

Add the m4340nhp bsp_tests.json and fw_util.json, and their ConfigLibTest checks.

Test Plan

The build-time config generator accepts both configs.

On a m4340nhp device, bsp_tests and fw_util_hw_test pass.