Fixed string replacement in metal shaders (#1537)

When we do string replacement for metal shaders we might replace the
wrong substring if the original sampler name had "Texture" in the name.
This is the reason why shadows currently don't work when using metal.

Author: SergioRZMasson

Plugins/NativeEngine/Source/ShaderCompilerMetal.cpp

@@ -49,13 +49,15 @@ namespace Babylon
                 compiler->set_name(resource.id, "_mtl_u");
             }
 
-            // rename textures without the 'texture' suffix so it's bindable from .js
+            // WebGL shaders use a single sampler uniform, Metal separates it into a sampler and a texture, appending "Texture" and "Sampler" to the original WebGL names.
+            // Remove 'Texture' from the uniform name to match JS expected names.
             for (auto& resource : resources.separate_images)
             {
                 std::string imageName = resource.name;
                 if (imageName.find("Texture") != std::string::npos)
                 {
-                    imageName.replace(imageName.find("Texture"), std::string::npos, "");
+                    // Using rfind ensures the correct "Texture" is removed from WebGL uniforms with "texture" in their original name. (e.g., "shadowTexture1")
+                    imageName.replace(imageName.rfind("Texture"), std::string::npos, "");
                     compiler->set_name(resource.id, imageName);
                 }
             }