fix deadlocks in RAIntegration for real this time (i hate this hack)

fixes f8a5adecb5

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -2296,6 +2296,8 @@ namespace BizHawk.Client.EmuHawk
 
 		private void CheckMessages()
 		{
+			using var raMemHack = (RA as RAIntegration)?.ThisIsTheRAMemHack();
+
 			Application.DoEvents();
 			if (ActiveForm != null)
 			{

src/BizHawk.Client.EmuHawk/RetroAchievements/RAIntegration.cs

@@ -281,5 +281,9 @@ namespace BizHawk.Client.EmuHawk
 				RA.DoAchievementsFrame();
 			}
 		}
+
+		// FIXME: THIS IS GARBAGE
+		public RAMemGuard.AccessWrapper? ThisIsTheRAMemHack()
+			=> _memGuard.GetAccess();
 	}
 }

src/BizHawk.Client.EmuHawk/RetroAchievements/RetroAchievements.Memory.cs

@@ -21,8 +21,8 @@ namespace BizHawk.Client.EmuHawk
 			{
 				lock (MemSync)
 				{
-					MemSema.Wait();
 					MemLock.Wait();
+					MemSema.Wait();
 				}
 			}
 
@@ -37,7 +37,8 @@ namespace BizHawk.Client.EmuHawk
 				MemSema.Dispose();
 			}
 
-			public readonly ref struct AccessWrapper
+			// can't be a ref struct due to ThisIsTheRAMemHack :(
+			public readonly struct AccessWrapper : IDisposable
 			{
 				private readonly RAMemGuard _guard;