fix(core): Fixes several serialization issues (#355)

- [X] Fixes an issue where a buffer smaller than 8 bytes would not double with enough space in some cases.
- [X] Fixes an issue with dupe copying the savebuffer reference (ugh).
- [X] Streamlines the IGenericWriter API to use better generics.
- [X] Streamlines the IGenericReader API to use better generics.
- [X] Forces `tidying` of a List/HashSet to be done externally since Writers/Readers should not have side effects.
- [X] Fixes an issue where Tidying a list didn't TrimExcess, causing memory leaks.
- [X] Reverted the meaning of `World.Running` to specifically refer to any world state post world loading.
  - NOTE: Do not use this if you want to block on world saves. Instead use checks against `WorldState.Saving` states.
- [X] Fixes an issue with serializing negative DateTime deltas.
- [X] Fixes a potential issue with serializing non-UTC DateTime.

Bumps release version

Projects/UOContent/Mobiles/Animals/Mounts/Ethereals.cs

@@ -256,7 +256,7 @@ namespace Server.Mobiles
                     {
                         m_MountedID = reader.ReadInt();
                         m_RegularID = reader.ReadInt();
-                        m_Rider = reader.ReadMobile();
+                        m_Rider = reader.ReadEntity<Mobile>();
 
                         if (m_MountedID == 0x3EA2)
                         {