Enable RCS1043 and fix noncompliance

"Remove 'partial' modifier from type with a single part"

.global.editorconfig.ini

@@ -397,6 +397,8 @@ dotnet_diagnostic.MEN018.severity = warning
 
 ## Roslynator.Analyzers rules
 
+# Remove 'partial' modifier from type with a single part
+dotnet_diagnostic.RCS1043.severity = warning
 # Avoid locking on publicly accessible instance
 dotnet_diagnostic.RCS1059.severity = silent
 # Avoid empty catch clause that catches System.Exception

src/BizHawk.Common/Extensions/SpanSplit.cs

@@ -759,7 +759,7 @@ namespace BizHawk.Common
 			}
 		}
 
-		private ref partial struct ValueListBuilder<T>
+		private ref struct ValueListBuilder<T>
 		{
 			private Span<T> _span;
 			private T[]? _arrayFromPool;

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/CRTC.cs

@@ -37,7 +37,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 	/// Datasheet:    {none}
 	///
 	/// </summary>
-	public abstract partial class CRTC : IPortIODevice
+	public abstract class CRTC : IPortIODevice
 	{
 		/// <summary>
 		/// Instantiation helper

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum128KPlus2/ZX128Plus2.cs

@@ -7,7 +7,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// The +2 is almost identical to the 128k from an emulation point of view
 	/// There are just a few small changes in the ROMs
 	/// </summary>
-	public partial class ZX128Plus2 : ZX128
+	public sealed class ZX128Plus2 : ZX128
 	{
 		/// <summary>
 		/// Main constructor