Feature: Support tracing for async functions

[heitorlessa]

Background

Issue, if applicable: aws-powertools/powertools-lambda#10

As of now, Tracer doesn't support async functions, meaning that any method or library (aioboto3) that makes use of the event loop won't be traced properly.

Implementation

Investigation needed - X-Ray SDK supports async function by introducing async context: https://docs.aws.amazon.com/xray/latest/devguide/xray-sdk-python-patching.html#xray-sdk-python-patching-async

[heitorlessa]

Released on 0.9.1 version