cscore: Change impl to only one singleton (#1398)

This avoids a number of shutdown use-after-free races by controlling the
destruction order.  It also is a prerequisite to making the internal
interfaces mockable for unit testing.

cscore/src/main/native/linux/UsbCameraImpl.h

@@ -31,9 +31,13 @@
 
 namespace cs {
 
+class Notifier;
+class Telemetry;
+
 class UsbCameraImpl : public SourceImpl {
  public:
-  UsbCameraImpl(const wpi::Twine& name, const wpi::Twine& path);
+  UsbCameraImpl(const wpi::Twine& name, wpi::Logger& logger, Notifier& notifier,
+                Telemetry& telemetry, const wpi::Twine& path);
   ~UsbCameraImpl() override;
 
   void Start();