Feature request: B3 propagation for python otel package

[Joas1988]

We are still using B3 context propagation for some of our APM coverered services. And b3 propagation package is missing in

https://github.com/open-telemetry/opentelemetry-lambda/tree/main/python/src/otel/otel_sdk

It should be fairly easy to add. Ref

https://github.com/open-telemetry/opentelemetry-python/tree/main/propagator/opentelemetry-propagator-b3

I would save us time of creating our own versions of layers, just because of propagation.

Any input appreciated.