Add OpenTelemetry span transformation

[sl0thentr0py]

Some SDKs (js/ruby/python/java) will soon start sending over transactions mapped over from OpenTelemetry spans.

The spans in these transactions will contain otel attributes as data. We want to add relay-side logic for mapping over some of these attributes to span ops/description/status so that we don't need to replicate this logic in each SDK.

This will also serve as a starting point for further adding more server-side otel compatibility logic which we can keep iterating on.

Implementation

For now, we will add the logic to normalize_spans which means this will be restricted to processing relays. Open questions remain on how to roll this out.