Metrics adapters no longer inject services.

I have a few custom adapters in my application that depend on injected services.

I've updated my app to use ember-metrics 2.0.0-beta.2 and am now seeing this error in the console when running the app:

> Uncaught (in promise) Error: Assertion Failed: Attempting to lookup an injected property on an object without a container, ensure that the object was instantiated via a container.

Proposing this change to the metrics service to fix this:

```
/**
* Instantiates an adapter.
*
* @method _activateAdapter
* @param {Object}
* @private
* @return {Adapter}
*/
_activateAdapter({ adapterClass, config }) {
const adapter = new adapterClass(config);
setOwner(adapter, getOwner(this));
adapter.install();
return adapter;
}
```

Start at the metrics service's _activateAdapter method shown in the issue and inspect how custom adapters are instantiated and activated. Verify the change against an application adapter that depends on injected services; done means the adapter can use those services without the reported container assertion.

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