Do a major cleanup in Collapse.js

• streamline _getConfig & interface
• Remove redundant check on data-toggle click, as it was assuming that trigger element would own separate config than the collapse itself (wasn't documented)
• Use helper function to check show
• Remove helper for isTransitioning
• Use forEach for all iterations
• refactor privatef unction to use it in more cases
• initialize array variable properly
• Simplify check for children and make it generic
• remove duplicated Selector.find
• keep parent only as element
• simplify initialization on data-toggle click
• transfer interface inside jQueryInterface

NOTE for reviewers:

Better review it, commit by commit. It will help you with the proper message and will guide you with sanity to follow the logic

Closes #34408 (closed)