Support for Cloudwatch logging via trace ID injection

Hi - with the release of ServiceLens (which looks very helpful), I was wondering if you were considering adding trace ID injection somehow? This is required to match Cloudwatch logs to traces in XRay (and thus ServiceLens), see [here](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/deploy_servicelens_CloudWatch_agent_logintegration.html).

This works in the XRay Java SDK by injecting the trace ID into the MDC (see [here](https://docs.aws.amazon.com/xray/latest/devguide//xray-sdk-java-configuration.html#xray-sdk-java-configuration-logging)), which means that each log is given a suffix that includes the trace ID (can then be picked up by the ServiceLens/XRay console to tie traces to logs), e.g. :

`2019-09-10 18:58:30.844 [nio-5000-exec-4] AWS-XRAY-TRACE-ID: 1-5d77f256-19f12e4eaa02e3f76c78f46a WARN 1 - Your logging message here`

Any thoughts on supporting this in the way that the Java SDK does? I don't know much about the MDC but I've only seen it in Java.

L’issue non indica file né test; inizia dalla documentazione collegata sul logging di CloudWatch ServiceLens e X-Ray Java SDK, quindi esamina le superfici esistenti di logging e contesto delle tracce del Python SDK. Il lavoro sarà considerato completato quando sarà definito un comportamento Python concordato per l’iniezione del trace-ID, verificato tramite un output di log in grado di associare le voci alle tracce X-Ray.

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