Add code sample for AWS Lambda with additional instrumentation

[davidkeaveny]

The samples folder gives a basic example of adding OpenTelemetry to AWS Lambda functions in .NET, which works fine for existing third-party libraries. However, it does not illustrate how to add your own instrumentation to the collected data.

The examples folder for the AspNetCore does illustrate how to add custom instrumentation, but the configuration process is relatively different to that required by the AWS Lambda (registering services on the IServiceCollection rather than calling Sdk.CreateTracerProviderBuilder(), for example).

Has anyone been able to get custom instrumentation up and running with AWS Lambda, and if so, would they be able to provide sample code?