Make Application Settings sections headers collapsible

What does this MR do and why?

Make Application Settings sections headers collapsible when the user clicks on them. I went over all sections in the Admin settings and added necessary classes.

Screenshots or screen recordings

Just some sections are recorded here:

admin_application_settings-2022-07-07_09.24.04

(Note: you could notice the section Maintenance mode is not collapsible. This is because we merged community contribution here which is not merged into my local branch yet)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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.