Missing TCK tests for Emitters + mpMetrics integration

[abutch3r]

The specification for Reactive Messaging's integration with mpMetrics is defined here https://download.eclipse.org/microprofile/microprofile-reactive-messaging-3.0/microprofile-reactive-messaging-spec-3.0.html#_metrics.

The Spec only mentions channels, in no way does it specify directionality, or especially in the case of outgoing channels how the messages are put effectively 'sent', whether it is via an emitter or an @Outgoing.

While reviewing the TCK, there are tests for the @Outgoing and @Incoming annotations to check the counts for each channel relating to them. However there are no tests for checking counts on channels which have an emitter associated with them. This can lead to a gap were an implementation might not count messages sent via an emitter onto a channel.

The test must emit messages to a connector, such that @Incoming does not itself update the channel count. the connector can put out to an @Incoming so that a comparison between messages having been put on the the outgoing channel meet those that reach the end of the stream