core: Make variable shadowing a compile-time error

Now that we have most of core free of shadowing, we can enable the
warning as an error to catch anything that may be remaining and also
eliminate this class of logic bug entirely.

src/core/hle/service/vi/layer/vi_layer.cpp

@@ -6,7 +6,7 @@
 
 namespace Service::VI {
 
-Layer::Layer(u64 id, NVFlinger::BufferQueue& queue) : id{id}, buffer_queue{queue} {}
+Layer::Layer(u64 id, NVFlinger::BufferQueue& queue) : layer_id{id}, buffer_queue{queue} {}
 
 Layer::~Layer() = default;
 

src/core/hle/service/vi/layer/vi_layer.h

@@ -31,7 +31,7 @@ public:
 
     /// Gets the ID for this layer.
     u64 GetID() const {
-        return id;
+        return layer_id;
     }
 
     /// Gets a reference to the buffer queue this layer is using.
@@ -45,7 +45,7 @@ public:
     }
 
 private:
-    u64 id;
+    u64 layer_id;
     NVFlinger::BufferQueue& buffer_queue;
 };