Seal MySqlCommandBuilder and MySqlConversionException.

These types were not designed for inheritance.

Author: bgrainger

src/MySqlConnector/MySqlCommandBuilder.cs

@@ -9,7 +9,7 @@
 
 namespace MySqlConnector
 {
-	public class MySqlCommandBuilder : DbCommandBuilder
+	public sealed class MySqlCommandBuilder : DbCommandBuilder
 	{
 		public static void DeriveParameters(MySqlCommand command) => DeriveParametersAsync(IOBehavior.Synchronous, command, CancellationToken.None).GetAwaiter().GetResult();
 		public static Task DeriveParametersAsync(MySqlCommand command) => DeriveParametersAsync(command?.Connection?.AsyncIOBehavior ?? IOBehavior.Asynchronous, command!, CancellationToken.None);

src/MySqlConnector/MySqlConversionException.cs

@@ -7,7 +7,7 @@ namespace MySqlConnector
 	/// <see cref="MySqlConversionException"/> is thrown when a MySQL value can't be converted to another type.
 	/// </summary>
 	[Serializable]
-	public class MySqlConversionException : Exception
+	public sealed class MySqlConversionException : Exception
 	{
 		/// <summary>
 		/// Initializes a new instance of <see cref="MySqlConversionException"/>.