Remove containers

[jrmoulton]

• Added an entry to CHANGELOG.md if this change could be valuable to users

This:

• Removes more of the extra containers
• Adds more debug names
• Removes drawing the scroll bar background in the editor view so that the editor view is consistent with the other tab views.

I've also made an opinionated change to the design of the border on editor tabs. They now fill the full height of the tab bar. This looks more clear and less busy to me, but that's just my opinion and if people actually prefer the old way I can make it configurable.

Also fixes 2883 which had been previously implemented but was not responding the config changes.
I misread that issue. But now editor tab close button responds to config changes

[dzhou121]

Could you please make the editor tab border configurable?