Added MySQL8Dialect and MySQL8InnoDBDialect (#3236)

Author: dennis-gr

src/NHibernate/Dialect/MySQL8Dialect.cs

@@ -0,0 +1,9 @@
+using System.Data;
+
+namespace NHibernate.Dialect
+{
+	public class MySQL8Dialect : MySQL57Dialect
+	{
+		public MySQL8Dialect() => RegisterColumnType(DbType.Boolean, "BOOLEAN");
+	}
+}

src/NHibernate/Dialect/MySQL8InnoDBDialect.cs

@@ -0,0 +1,11 @@
+namespace NHibernate.Dialect
+{
+	public class MySQL8InnoDBDialect : MySQL8Dialect
+	{
+		public override bool SupportsCascadeDelete => true;
+
+		public override string TableTypeString => " ENGINE=InnoDB";
+
+		public override bool HasSelfReferentialForeignKeyBug => true;
+	}
+}