Add unit tests for OTel context propagation on gRPC requests

For context, see https://github.com/rigetti/qcs-sdk-rust/pull/544#discussion_r2010348602

Goal:

Test that the traceparent metadata on execution and translation requests is set; assert that the value contains the hex representation of the OTel context trace id from the calling Python OTel span.

How:

1. We need to fuller configurability TracingConfiguration that TracingConfiguration::from_env offers. See qcs-api-client-common issue 109 for some potential options.
2. In the test_tracing_subscriber test module, add a test test_translation_submit_and_retrieve_grpc_trace_propagation. The TracingConfiguration should include the traceparent metadata key in the request metadata keys to ascribe as an attribute on the span.
3. After reading the traces from file, look up the rpc.grpc.request.metadata.traceparent attribute on the gRPC spans; ensure that the value of this attribute contains the hex representation of the Python span's trace identifier.

Start in the test_tracing_subscriber test module and review TracingConfiguration::from_env, along with qcs-api-client-common issue 109 and the referenced pull-request discussion. Configure the request metadata keys, run the translation and execution request tests, and inspect the traces read from file. Done means the gRPC span's rpc.grpc.request.metadata.traceparent attribute contains the Python OTel span's trace identifier in hexadecimal.