Attach Otel context in the handler execution context

[slinkydeveloper]

see https://github.com/restatedev/restate/issues/1279

[slinkydeveloper]

Java implementation: https://github.com/restatedev/sdk-java/commit/a3c429152ddac3dd9d25bde0c5b52c0188a967e3

In Java we expose it in two ways:

• Attaching the current otel context to the thread-local/coroutine context. This is an expectation for server libraries using otel.
• Also give the otel context in the ctx.request() object

[igalshilman]

I’ll consider it close for now, perhaps we need to follow up with an example of how to setup OTEL within your handler, the trace context is accessible via ctx.request().attemptHeaders