The setting will now correctly open a new window when no file is specified, but if
a file is specified it will reuse. This is so opening via the file manager will reuse
the window.

Fixes #19775

Window opens in fullscreen when window.newWindowDimensions set to inherit or fullscreen (fixes #19628)

Fixes #19285

fixes #17343

allow users to toggle between git and preview SCM

- Extend search across left and right editors
- Show tabs inside settings editor to show user and workspace settings
- Improve highlighting of settings

This allows shift+click/middle+click/num+super Windows and Unity shortcuts to
work as expected while not changing regular launch behavior.

Part of #48