Refactor pipeline_details_bundle.js to break out functions

What does this MR do?

This is a precursor to adding the new DAG view (see: #215517 (closed)), which just adds the app/assets/javascripts/pipelines/pipeline_details_bundle.js refactor. It breaks the various Vue app ⚗ creation incantations ✨ into their own functions, to make the file a little easier to read and to make it clearer how the various apps are tied together.

Screenshots

There are no changes to visuals or behavior.

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Style guides