[Core] Tracing updates

[pvaneck]

Additional context: https://gist.github.com/pvaneck/12273663942e70e71cea36bf40716d8d

This introduces native OpenTelemetry tracing to Azure Core. This is intended to be an alternative/replacement to the azure-core-tracing-opentelemetry plugin.

To enable native OpenTelemetry tracing, users need to:

1. Have opentelemetry-api installed.
2. Ensure that settings.tracing_implementation is not set.
3. Ensure that settings.tracing_enabled is set to True.

If setting.tracing_implementation is set, the tracing plugin will be used instead of the native tracing. If settings.tracing_enabled is set to False, tracing will be disabled.

Main changes

• opentelemetry-api is added as an optional dependency, and is needed to enable native tracing.
• The OpenTelemetryTracer class was added to the azure.core.tracing.opentelemetry module. This is a wrapper around the OpenTelemetry tracer that is used to create spans for Azure SDK operations.
• Added a get_tracer method to the new azure.core.instrumentation module. This method returns an instance of the OpenTelemetryTracer class.
• A TracingOptions TypedDict class was added to define the options that SDK users can use to configure tracing per-operation. These options include the ability to enable or disable tracing and set additional attributes on spans.
  - Example usage: client.method(tracing_options={"enabled": True, "attributes": {"foo": "bar"}})
• The DistributedTracingPolicy and distributed_trace/distributed_trace_async decorators now uses the OpenTelemetry tracer if it is available and native tracing is enabled.
  • SDK clients can define an _instrumentation_config class variable to configure the OpenTelemetry tracer used in method span creation. Possible configuration options are library_name, library_version, schema_url, and attributes.
  • DistributedTracingPolicy now accepts a instrumentation_config keyword argument to configure the OpenTelemetry tracer used in HTTP span creation.

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

azure-core

[lmolkova]

It looks great - thanks a lot for putting it together!

Left some naming suggestions and other minor suggestions

[kristapratico]

Mostly nits and questions 🐱

[pvaneck]

Thanks, @kristapratico, for the feedback!

[pvaneck]

Verified that the azure-core-tracing-opentelemetry live tests still work with these changes. Adding live tests for native tracing here: #39945