Expose SystemTask dependency controllers

Expose NotificationManager and Settings for use by the feature in next commit.

This is a memory efficient way for accessing SystemTask dependencies from
controllers that have SystemTask injected as a dependency.
Looks like each direct dependency injection uses 4 bytes RAM.
As InfiniTime is close to running out of RAM (using 16 more bytes causes build
to fail with "ld: region RAM overflowed with stack") it might be helpful to use
this approach more.

src/systemtask/SystemTask.h

@@ -90,6 +90,14 @@ namespace Pinetime {
         return nimbleController;
       };
 
+      Pinetime::Controllers::NotificationManager& GetNotificationManager() {
+        return notificationManager;
+      };
+
+      Pinetime::Controllers::Settings& GetSettings() {
+        return settingsController;
+      };
+
       bool IsSleeping() const {
         return state == SystemTaskState::Sleeping || state == SystemTaskState::WakingUp;
       }