constructor() {
    if (RuntimeSettings._instance) return RuntimeSettings._instance;
    RuntimeSettings._instance = this;
    return this;
  }
Runtime settings are used to configure the collector per-request.
These settings are persisted across requests, but can be overridden per-request.

The settings are passed in the request body via `options.runtimeSettings`
which is set in the backend #attachOptions function in CollectorApi.

We do this so that the collector and backend can share the same ENV variables
but only pass the relevant settings to the collector per-request and be able to
access them across the collector via a single instance of RuntimeSettings.

TODO: We may want to set all options passed from backend to collector here,
but for now - we are only setting the runtime settings specifically for backwards
compatibility with existing CollectorApi usage.