Implement PIMPL pattern for TrayManager in Linux and macOS

- Introduced a private implementation (PIMPL) class for TrayManager to enhance encapsulation.
- Updated constructor to initialize the PIMPL instance, improving code organization and maintainability.

Author: lijy91

src/platform/linux/tray_manager_linux.cpp

@@ -19,7 +19,13 @@
 
 namespace nativeapi {
 
-TrayManager::TrayManager() : next_tray_id_(1) {}
+class TrayManager::Impl {
+ public:
+  Impl() {}
+  ~Impl() {}
+};
+
+TrayManager::TrayManager() : next_tray_id_(1), pimpl_(std::make_unique<Impl>()) {}
 
 TrayManager::~TrayManager() {
   std::lock_guard<std::mutex> lock(mutex_);

src/platform/macos/tray_manager_macos.mm

@@ -11,7 +11,13 @@
 
 namespace nativeapi {
 
-TrayManager::TrayManager() : next_tray_id_(1) {}
+class TrayManager::Impl {
+ public:
+  Impl() {}
+  ~Impl() {}
+};
+
+TrayManager::TrayManager() : next_tray_id_(1), pimpl_(std::make_unique<Impl>()) {}
 
 TrayManager::~TrayManager() {
   std::lock_guard<std::mutex> lock(mutex_);