Add AWS X-Ray Lambda Propagation Logic

[jj22ee]

xray-lambda propagation functionality is described in: https://opentelemetry.io/docs/specs/semconv/faas/aws-lambda/#xray-lambda-propagator-functionality

The existing OTel Ruby AWS Lambda Instrumentation currently cannot extract the trace context contained in Lambda's _X_AMZN_TRACE_ID Environment Variable. This is needed to link the AWS Lambda Span to the Traces generated by Lambda Service.

The xray-lambda propagation logic exists in some other OTel languages, but have different implementation locations:

• xray-lambda logic is in aws_lambda (Golang, .NET)
• xray-lambda logic is in its own package (Node.js)
• xray-lambda logic is part of AWS XRay Propagator (Java, Python)

I think it should be okay to follow the third case, where the xray-lambda propagator is part of the xray propagator package.

[yiyuan-he]

Thanks @jj22ee. I'll start looking into this.

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