Allow monitor script to be run without requiring snowplow-micro

What does this MR do and why?

Reintroduces !155848 (merged), which was previously reverted in !157064 (merged) due to a failing spec that caused a broken master.

The spec has now been updated in ef3a7ee8 and is passing.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

bundle exec rspec spec/scripts/internal_events/cli_spec.rb:665