[harmony] Add an icepyx harmony-py label to all requests

[asteiker]

In order to properly track metrics on icepyx usage, we need to add a label to our Harmony requests coming from this library. Otherwise they will only be labeled with "harmony-py" and would be misleading as the primary access point.

It looks like the Harmony team has a ticket this quarter to make it possible for an end-user to add an additional label: https://bugs.earthdata.nasa.gov/browse/HARMONY-1898. We may need to wait until this is implemented. Otherwise it shuold hopefully just require the addition of a new label parameter to be added to all requests.