Add additional properties to events in the Internal Events CLI

What does this MR do and why?

Adds handling for additional properties to Internal Events CLI. This MR handles collecting property descriptions and writing them to event definition files.

Out of scope: Support for writing filters to metrics definition files. This will happen in a separate MR.

Related issue: #434506

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.

Screenshots

How to set up and validate locally

1. Run ruby scripts/internal_events/cli.rb from the gitlab/ directory (gdk does not need to be running)
2. Go through the flow to create an event with additional properties
   • ex) include the status with an event like issue_status_changed