[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

Implements asic_config_v3 design.

In this PR, support all four AsicConfigGenType values.

• The platform schema accepts BENCHMARK and LINK_TEST in addition to DEFAULT and HW_TEST.
• The content validator reads BENCHMARK references from fboss/oss/hw_bench_configs and LINK_TEST references from fboss/oss/link_test_configs.

Also made change in the generator so that config_gen_type is fully data-driven.

• The uncached port statistics setting for the test profiles moves from the Tomahawk5 ASIC file into the wedge800bact and montblanc platform files, keyed on HW_TEST and LINK_TEST.
  This confirms to the design that the ASIC file describes the silicon and platform file decides what a test profile needs.

This PR is stacked on #1736

Test Plan

Regenerated every platform with the asic_config_v3 generator. The only outputs that changed are the two hw_test.yml files, where sai_uncached_port_stats moves after the keys written by the ASIC-level conditional settings.

Ran the content validator:

Summary:
  Platforms: 9
  Variants: 14
  BYTE_MATCH: 9
  SEMANTIC_MATCH: 5
  CONTENT_MISMATCH: 0

Validated the ASIC and platform configs against the schemas:

15 passed, 0 failed