feat(api): prepare V2 API with a healthcheck endpoint

[wescopeland]

This PR is a basic housekeeping PR to prepare the V2 Web API:

• Changes internal-api.php config to a more general-purpose api.php config file.
• Lifts up HealthController so it's used by both the Internal API and V2 Web API.

How to test this PR:

curl --request GET \
  --url http://localhost:64000/api/v2/health \
  --header 'X-API-Key: {redacted}'

Next steps:

• The V2 API needs to support multiauth with both Passport (OAuth2) and the X-API-Key header. (foundational work for this has started in feat: add the foundation for OAuth2 with Laravel Passport #4164)
• We need a search endpoint.
• We need an endpoint to expose games that belong to hubs.

I'm not going to open any documentation PRs over in api-docs for the first few commits into the V2 API. The first endpoint or two will likely be heavily subject to change.

[Jamiras]

internal/health and v2/health are both functional. the first is restricted properly.