Issue Type: Feature Request

• Toggle Centered Layout
• When there is two editor groups, the centered layout is turned off
• When there is only one editor group, the centered layout is activated automatically
• When a diff editor is opened, it's still in centered layout however the width for editor group is too small for two editors side by side, even though they are in the same editor group.

VS Code version: Code - Insiders 1.44.0-insider (e8dbc5e, 2020-04-03T22:09:44.908Z)
OS version: Darwin x64 19.2.0