Add second tray icon and update references

Add new tray icon assets (icons/icon2.ico, icons/icon2.png, icons/icon2.svg) and update example and tests to use icon2.png as TRAY_ICON2. Also replace/refresh existing icon.ico and icon.png binaries. This enables using a distinct second icon in the example and unit tests.

Author: ReenigneArcher

icons/icon.ico

@@ -10,7 +10,7 @@
 #include "tray.h"
 
 #define TRAY_ICON1 "icon.png"  ///< Path to first icon.
-#define TRAY_ICON2 "icon.png"  ///< Path to second icon.
+#define TRAY_ICON2 "icon2.png"  ///< Path to second icon.
 
 static struct tray tray;
 

icons/icon.png

@@ -16,7 +16,7 @@
 #include "tests/screenshot_utils.h"
 
 constexpr const char *TRAY_ICON1 = "icon.png";
-constexpr const char *TRAY_ICON2 = "icon.png";
+constexpr const char *TRAY_ICON2 = "icon2.png";
 constexpr const char *TRAY_ICON_SVG = "icon.svg";
 constexpr const char *TRAY_ICON_THEMED = "mail-message-new";