Add a separate configuration option for auto creating a log group

[cristian-radu]

I feel like log streams are more dynamic in nature so creating them automatically makes a lot of sense to me.

For example, we use a separate log stream per EC2 instance. However, log groups are fairly static in my environment. We have one per application and would rather manage these through IaC tooling.

It came as a surprise to me that the auto_create_stream option also creates the log group since that is not what the name would suggest. (admittedly, I should have read the docs here more carefully)

I propose adding an "auto_create_group" option as a separate feature.

It may be a breaking change for some deployments, but feels like users should have the option to choose what logging components to auto-create.

Unit tests fail on ruby 2.5, but this is EOL so ignored them.

Not deployed this anywhere yet. Will test it when I get a chance.