Handle context timeouts

### What problem are you facing?

I _think_ gRPC will propagate any deadline set by the client to the `context.Context` our `RunFunction` method is passed. It's unclear to me whether we have to check manually whether the deadline was exceeded before we run the Function, or whether gRPC will take care of that for us.

https://grpc.io/docs/what-is-grpc/core-concepts/#deadlines

### How could Crossplane help solve your problem?

Determine whether we need to be concerned with cancelled deadlines, and if so perhaps add a RunFunction wrapper that handles them (i.e. by avoiding doing work we don't need to do).