Fix bugs related breakpoints using the "icon border"

Before this MR, if you try setting a breakpoint using the "icon border", the breakpoint appears in the GUI, but if you run the debugger, it won't stop in the desired location.

Before this MR, if you set a breakpoint in a given file, then close the file and then open it again, the breakpoint will be invisible (but set).

Also, I changed the default breakpoint icon while the "new one" isn't merged on Breeze-Icons.