[cscore] Add support for USB cameras on macOS (#4846)

The main restriction is there must be an event loop running on the main thread.
No special action is required for GUI applications, but for non-GUI applications, a
RunOsxRunLoop() function is provided that needs to be called from the main thread.

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

@@ -0,0 +1,96 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#import <AVFoundation/AVFoundation.h>
+#import "UsbCameraDelegate.h"
+#import "UsbCameraImplObjc.h"
+
+#include <memory>
+#include <string>
+#include <optional>
+
+#include "SourceImpl.h"
+
+namespace cs {
+struct CameraFPSRange {
+  int min;
+  int max;
+
+  bool IsWithinRange(int fps) { return fps >= min && fps <= max; }
+};
+
+struct CameraModeStore {
+  VideoMode mode;
+  AVCaptureDeviceFormat* format;
+  std::vector<CameraFPSRange> fpsRanges;
+};
+
+class UsbCameraImpl : public SourceImpl {
+ public:
+  UsbCameraImpl(std::string_view name, wpi::Logger& logger, Notifier& notifier,
+                Telemetry& telemetry, std::string_view path);
+  UsbCameraImpl(std::string_view name, wpi::Logger& logger, Notifier& notifier,
+                Telemetry& telemetry, int deviceId);
+  ~UsbCameraImpl() override;
+
+  void Start() override;
+
+  // Property functions
+  void SetProperty(int property, int value, CS_Status* status) override;
+  void SetStringProperty(int property, std::string_view value,
+                         CS_Status* status) override;
+
+  // Standard common camera properties
+  void SetBrightness(int brightness, CS_Status* status) override;
+  int GetBrightness(CS_Status* status) const override;
+  void SetWhiteBalanceAuto(CS_Status* status) override;
+  void SetWhiteBalanceHoldCurrent(CS_Status* status) override;
+  void SetWhiteBalanceManual(int value, CS_Status* status) override;
+  void SetExposureAuto(CS_Status* status) override;
+  void SetExposureHoldCurrent(CS_Status* status) override;
+  void SetExposureManual(int value, CS_Status* status) override;
+
+  bool SetVideoMode(const VideoMode& mode, CS_Status* status) override;
+  bool SetPixelFormat(VideoMode::PixelFormat pixelFormat,
+                      CS_Status* status) override;
+  bool SetResolution(int width, int height, CS_Status* status) override;
+  bool SetFPS(int fps, CS_Status* status) override;
+
+  void NumSinksChanged() override;
+  void NumSinksEnabledChanged() override;
+
+  cs::Notifier& objcGetNotifier() { return m_notifier; }
+
+  void objcSwapVideoModes(std::vector<VideoMode>& modes) {
+    std::scoped_lock lock(m_mutex);
+    m_videoModes.swap(modes);
+  }
+
+  void objcSetVideoMode(const VideoMode& mode) {
+    std::scoped_lock lock(m_mutex);
+    m_mode = mode;
+  }
+
+  void objcPutFrame(std::unique_ptr<Image> image, Frame::Time time) {
+    PutFrame(std::move(image), time);
+  }
+
+  const VideoMode& objcGetVideoMode() const { return m_mode; }
+
+  std::vector<CameraModeStore>& objcGetPlatformVideoModes() {
+    return m_platformModes;
+  }
+
+  wpi::Logger& objcGetLogger() { return m_logger; }
+
+  UsbCameraImplObjc* cppGetObjc() { return m_objc; }
+
+ private:
+  UsbCameraImplObjc* m_objc;
+  std::vector<CameraModeStore> m_platformModes;
+  VideoMode m_mode;
+};
+}  // namespace cs