Allow setting of mode also for function breakpoints #539

Some debuggers (e.g. LLDB) can create function breakpoints in multiple different modes (software/hardware). At the moment DAP can not express this as the FunctionBreakpoint type is missing the mode parameter present on other breakpoint types.

Was there some specific reason for not allowing the mode on the FunctionBreakpoint?

Is there some other, standard way that mode of function breakpoint can be passed to the DA?

If both of the above are false please consider adding the mode parameter onto the FunctionBreakpoint type