Bugzilla

It should be possible to add the generated metrics to the base `Glean`  class, using it like a namespace, by using [extensions](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html).  According to the docs for extensions, we can add new nested types, which would mean we could generate something like:

```Swift
extension Glean {
    internal enum GleanInternalMetrics {
        /// The name of the operating system.
        static let os = StringMetricType(
            category: "",
            name: "os",
            sendInPings: ["glean_client_info"],
            lifetime: .application,
            disabled: false
        )
        ...
    }
}
```

It should be possible to add the generated metrics to the base `Glean`  class, using it like a namespace, by using [extensions](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html).  According to the docs for extensions, we can add new nested types, which would mean we could generate something like:

```Swift
extension Glean {
    internal enum GleanInternalMetrics {
        /// The name of the operating system.
        static let os = StringMetricType(
            category: "",
            name: "os",
            sendInPings: ["glean_client_info"],
            lifetime: .application,
            disabled: false
        )
        ...
    }
}
```

Or we could create a new base class like a struct/enum, but it would have to be named something other than `Glean` to prevent clashing with the Glean internal API class.