Add pirate metrics Activation helpers

[kkostov]

This PR adds the following helper methods:

/**
    * Send a `TelemetryDeck.Activation.onboardingCompleted` signal.
    */
fun onboardingCompleted(params: Map<String, String> = emptyMap(), customUserID: String? = null)

/**
    * Send a `TelemetryDeck.Activation.coreFeatureUsed` signal.
    */
fun coreFeatureUsed(
    featureName: String,
    params: Map<String, String> = emptyMap(),
    customUserID: String? = null
)