Expand the index cache to a generous size

This seems to slightly increase performance in Crash Nitro Kart
which can do ~4000 draws per frame

src/core/hle/D3D8/Direct3D9/Direct3D9.cpp

@@ -2702,7 +2702,7 @@ ConvertedIndexBuffer& CxbxUpdateActiveIndexBuffer
 	}
 
 	// Poor-mans eviction policy : when exceeding treshold, clear entire cache :
-	if (g_IndexBufferCache.size() > 256) {
+	if (g_IndexBufferCache.size() > 10000) {
 		g_IndexBufferCache.clear(); // Note : ConvertedIndexBuffer destructor will release any assigned pHostIndexBuffer
 	}