[lldb] Replace NativeProcess delegate list with a single delegate

In all this time, we've never used more than one delegate. The logic to
support multiple delegates is therefore untested, and becomes
particularly unwieldy once we need to support multiple processes.

Just remove it.

lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp

@@ -1018,7 +1018,7 @@ void NativeProcessNetBSD::MonitorClone(::pid_t child_pid) {
 
   MainLoop unused_loop;
   NativeProcessNetBSD child_process{static_cast<::pid_t>(child_pid),
-                                    m_terminal_fd, *m_delegates[0], m_arch,
+                                    m_terminal_fd, m_delegate, m_arch,
                                     unused_loop};
   child_process.Detach();
   Status pt_error =