add support for `service.version` and `service.environment` with apmInstrumentation

[trentm]

service.version, at least, has been added to the ecs-logging spec:
https://github.com/elastic/ecs-logging/blob/d8ee4d4ba5853a10425ac21f41a5ff04f84b355b/spec/spec.json#L88-L96
with the comment that:

When an APM agent is active, it should auto-configure it if not already set.

The spec will be sync'd here with #120.

Then ecs-logging-java added support for service.version and service.environment:

• Added support for service.version ecs-logging-java#168
• Add support for service.environment ecs-logging-java#184

Should the node.js ecs-logging libs do the same?

[trentm]

This adds service.environment to the spec as well now: #123