deps: update to iroh 0.35 and iroh-metrics 0.34 (#16)

Updates to `iroh`, `iroh-blobs` and `iroh-gossip` to 0.35. Also updatesi iroh-metrics and adapts the metrics collection.

This still uses the openmetrics text format on the wire, however the `EndpointMetrics` now implement Serialize and Deserialize, so likely we want to use that, the savings in bytes is enourmous.

Author: Frando