Smaller gutter width: combine breakpoints/folds with numbers

[eugenesvk]

Gutter takes too much space with the empty space for what potentially can only be, but doesn't exist yet (like breakpoints). Instead of being wide, those should be very narrow, but allow for a brighter color for better visibility, and then part of the line number itself should be used for mouse actions

For example, •123 breakpoint with a line number clicking anywhere on •12 should be equivalent to clicking on the breakpoint symbol

Similarly, instead of having wide folds V you could have a much smaller ↓ fit in the line number padding 123↓ and then pressing 23↓ should collapse, but change symbol from a wide > to again something more narrow but with a customizable color so you could retain the status visibility

If you allow for custom removal of padding, this could save ~50% of the current whitespaced non-numerical width