Codefix: Move provider instances to static members. (#14501)

Avoids misnaming in global scope.

src/screenshot_bmp.cpp

@@ -145,6 +145,9 @@ public:
 
 		return true;
 	}
+
+private:
+	static ScreenshotProvider_Bmp instance;
 };
 
-static ScreenshotProvider_Bmp s_screenshot_provider_bmp;
+/* static */ ScreenshotProvider_Bmp ScreenshotProvider_Bmp::instance{};

src/screenshot_pcx.cpp

@@ -149,6 +149,9 @@ public:
 
 		return success;
 	}
+
+private:
+	static ScreenshotProvider_Pcx instance;
 };
 
-static const ScreenshotProvider_Pcx s_screenshot_provider_pcx;
+/* static */ ScreenshotProvider_Pcx ScreenshotProvider_Pcx::instance{};

src/screenshot_png.cpp

@@ -177,6 +177,9 @@ private:
 	{
 		Debug(misc, 1, "[libpng] warning: {} - {}", message, *static_cast<std::string_view *>(png_get_error_ptr(png_ptr)));
 	}
+
+private:
+	static ScreenshotProvider_Png instance;
 };
 
-static ScreenshotProvider_Png s_screenshot_provider_png;
+/* static */ ScreenshotProvider_Png ScreenshotProvider_Png::instance{};

src/soundloader_opus.cpp

@@ -83,6 +83,9 @@ public:
 
 		return true;
 	}
+
+private:
+	static SoundLoader_Opus instance;
 };
 
-static SoundLoader_Opus s_sound_loader_opus;
+/* static */ SoundLoader_Opus SoundLoader_Opus::instance{};

src/soundloader_raw.cpp

@@ -47,6 +47,9 @@ public:
 
 		return true;
 	}
+
+private:
+	static SoundLoader_Raw instance;
 };
 
-static SoundLoader_Raw s_sound_loader_raw;
+/* static */ SoundLoader_Raw SoundLoader_Raw::instance{};

src/soundloader_wav.cpp

@@ -96,6 +96,9 @@ public:
 
 		return false;
 	}
+
+private:
+	static SoundLoader_Wav instance;
 };
 
-static SoundLoader_Wav s_sound_loader_wav;
+/* static */ SoundLoader_Wav SoundLoader_Wav::instance{};