Code folding doesn't play well with View > Line Numbers toggle

[peterflynn]

1. Uncheck View > Line Numbers
   • Result: code folding triangles are too close to the left edge of the editor -- need more padding
2. Re-check View > Line Numbers
   • Result: code folding is on the left of the line numbers now -- should be to the right

This seems relatively edge-casey, to the point where I could envision shipping 1.3 without fixing this. I suspect most people who have line numbers hidden will also want folding triangles hidden, and they're unlikely to re-enable line numbers afterward (and issue 2 is easy to work around).

[VitorLuizC]

The same problem happens in Brackets 1.4

[petetnt]

Fixed in #12673