[TrackMetric] The `average` of the `trackMetric` call is sent as `value` which seems wrong

[MSNev]

The current trackMetric API takes an object where the property average shows up in the portal as valueSum and the internal documentation states that it is the value or average.

We need to

• investigate whether this can still be defined as the "average" and stored in the Portal as an "average" value
• If it's always a value or if "can" be either, then we "should" add another optional property (to keep backward compatibility) to provide average or value and if both are provided then it should "prefer" the average (unless the above investigation identifies the specific case / reason why it's either)

Adding and tagging as an enhancement to review as part of the backlog when we have cycles to investigate further.