Smaller initial size for ModifiedRangeList & directly inherit range list (#2663)

This fixes a potential regression with the new range list changes, where the cost for creating new ones would be rather large due to creating a 1024 size array. Also reduces cost for range list inheritance by using the first existing range list as a base, rather than creating a new one then adding both lists to it.

The growth size for the RangeList is now identical to its initial size. Every 32 elements was probably a little too common - now it is 1024 for most things and 8 for the buffer modified range list.

The Unmapped and SyncMethod methods have been changed to ensure that they behave properly if the range list is set null. Cleaned up a few calls to use the null-conditional operator.

Ryujinx.Graphics.Gpu/Memory/BufferModifiedRangeList.cs

@@ -60,6 +60,8 @@ namespace Ryujinx.Graphics.Gpu.Memory
     /// </summary>
     class BufferModifiedRangeList : RangeList<BufferModifiedRange>
     {
+        private const int BackingInitialSize = 8;
+
         private GpuContext _context;
 
         private object _lock = new object();
@@ -68,7 +70,7 @@ namespace Ryujinx.Graphics.Gpu.Memory
         /// Creates a new instance of a modified range list.
         /// </summary>
         /// <param name="context">GPU context that the buffer range list belongs to</param>
-        public BufferModifiedRangeList(GpuContext context)
+        public BufferModifiedRangeList(GpuContext context) : base(BackingInitialSize)
         {
             _context = context;
         }