expose a possible IMonitor for memory domains, use it to speed up RAM Search for waterbox cores (25-30% speedup?)

see #3296

src/BizHawk.Client.Common/tools/RamSearchEngine/RamSearchEngine.cs

@@ -198,10 +198,18 @@ namespace BizHawk.Client.Common.RamSearchEngine
 		{
 			if (_settings.IsDetailed())
 			{
-				foreach (IMiniWatchDetails watch in _watchList)
-				{
-					watch.Update(_settings.PreviousType, _settings.Domain, _settings.BigEndian);
+				try
+				{
+					_settings.Domain.Monitor?.Enter();
+					foreach (IMiniWatchDetails watch in _watchList)
+					{
+						watch.Update(_settings.PreviousType, _settings.Domain, _settings.BigEndian);
+					}
 				}
+				finally
+				{
+					_settings.Domain.Monitor?.Exit();
+				}	
 			}
 		}
 

src/BizHawk.Emulation.Common/Base Implementations/MemoryDomain.cs

@@ -27,6 +27,12 @@ namespace BizHawk.Emulation.Common
 
 		public bool Writable { get; protected set; }
 
+		/// <summary>
+		/// only use this if you are expecting to do a lot of peeks/pokes
+		/// MAY BE NULL
+		/// </summary>
+		public IMonitor Monitor { get; protected set; }
+
 		public abstract byte PeekByte(long addr);
 
 		public abstract void PokeByte(long addr, byte val);

src/BizHawk.Emulation.Cores/Waterbox/WaterboxMemoryDomain.cs

@@ -51,6 +51,7 @@ namespace BizHawk.Emulation.Cores.Waterbox
 				_addressMangler = 0;
 			}
 			Definition = m;
+			Monitor = _monitor;
 		}
 	}