Add V8 isolate ID to traces

Motivation:

Cloudflare may co-locate multiple Durable Objects in a single V8 isolate. Certain failures (e.g. exceeding CPU or memory limits) may propagate and terminate all Durable Objects within the same V8 isolate.

Assigning a unique ID per V8 isolate will simplify debugging by making it easy to query all traces that happened within the same isolate.