Remove `notify_only_broken_pipelines` patch

What does this MR do and why?

We're removing the undef :notify_only_broken_pipelines code from the integrations, as well as the boolean_accessor part.

In addition, we're moving the sections to the parent class.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Checkout the branch
2. Visit the integrations' page
3. Open some chat integrations (e.g. Telegram, Webex, Discord, etc.)
4. Validate that everything works as expected, and new "sections" part is visible 🎉

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.