Swift / Core Metrics integration

[AdonisCodes]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
Currently the OpenAI client doesn't have any way to track stuff via prometheus / any other metric aggregator. I would like to see some feature implementing swift-metrics into the client.

The great thing about swift-metrics is that it gets ignored by default unless you setup some aggregator.

Describe alternatives you've considered
Before & After each client call adding a self created metric, gets annoying & requires me to write a thin wrapper over this entire package, which isn't ideal!

Additional context
I would love to integrate this if I can get the green light!