Add method ordering guideline to Ruby style guide

What does this MR do and why?

Add method ordering guideline to Ruby style guide

Add a new section to the Ruby style guide documenting the recommended practice of ordering methods by level of abstraction within classes.

The guideline recommends placing higher-level orchestrator methods before the lower-level helper methods they call, following the "newspaper style" or "stepdown rule" principle. This helps readers understand what the code does before diving into implementation details.