Allow forcing ingestion key

[schmurfy]

I would like to be able to set the ingestion api key when deploying the app, I don't really understand what the logic is to consider this as a security risk when the key ends up in an environment variable anyway.

The key would come from a secret in our usecase and it just allows us to install otel-collector and hyperdx without having to first let it generate a random key and then redeploy it by setting it in the collector config.