Codechange: Replace pointer to Sprite array with reference to SpriteCollection. (#11580)

Add `SpriteLoader::SpriteCollection` type which is an array of `SpriteLoad::Sprite`.

This removes the ambiguity of what `SpriteLoader::Sprite *` is pointing to,
and cleans up mismatches using both dereference -> and array access [] for the
same object.

src/blitter/32bpp_sse2.hpp

@@ -76,7 +76,7 @@ public:
 		byte data[]; ///< Data, all zoomlevels.
 	};
 
-	Sprite *Encode(const SpriteLoader::Sprite *sprite, AllocatorProc *allocator);
+	Sprite *Encode(const SpriteLoader::SpriteCollection &sprite, AllocatorProc *allocator);
 };
 
 DECLARE_ENUM_AS_BIT_SET(Blitter_32bppSSE_Base::SpriteFlags);
@@ -88,7 +88,7 @@ public:
 	template <BlitterMode mode, Blitter_32bppSSE_Base::ReadMode read_mode, Blitter_32bppSSE_Base::BlockType bt_last, bool translucent>
 	void Draw(const Blitter::BlitterParams *bp, ZoomLevel zoom);
 
-	Sprite *Encode(const SpriteLoader::Sprite *sprite, AllocatorProc *allocator) override {
+	Sprite *Encode(const SpriteLoader::SpriteCollection &sprite, AllocatorProc *allocator) override {
 		return Blitter_32bppSSE_Base::Encode(sprite, allocator);
 	}