Provide service and instance metadata at runtime via environment variables

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**Tell us about your request**
What do you want us to build?

It would be incredibly useful for an instance to identify basic metadata about itself, i.e. the service name, ID, and instance ID.

Most importantly, the instance ID gives the instance a means to identify itself uniquely alongside other instances when connecting to a 3rd party service.

In my use case, this would be connecting to AWS IoT Core MQTT Broker with a unique client ID that is easily correlated to a running instance.

In Heroku, there are a number of metadata environment variables that are available to 'dynos' (instances) to help it identify itself. See https://devcenter.heroku.com/articles/dyno-metadata#dyno-metadata

These environment variables are also useful for logging purposes, as well as identifying when the code is being run in a hosted environment.

**Describe alternatives you've considered**

I'm still trying to come up with alternatives to the techniques we've used with Heroku environment variables, in hopes that we can migrate to App Runner.

**Additional context**
Anything else we should know?

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