[Instrumentation.AWSLambda] Incoming FaaS Span attributes: detect and set attribute for cold start

[rypdal]

Component

OpenTelemetry.Instrumentation.AWSLambda

Is your feature request related to a problem?

AWS Lambda instrumentation sets required incoming FaaS Span attribute faas.trigger. It would be useful also to set recommended faas.coldstart. See https://github.com/open-telemetry/semantic-conventions/blob/main/docs/faas/faas-spans.md#incoming-faas-span-attributes

What is the expected behavior?

Cold start is detected and the attribute faas.coldstart is set.

Which alternative solutions or features have you considered?

Not required.

Additional context

No response