Change migration SQL to include CASCADE for CREATE EXTENSION (#3684)

Closes #3682

Author: mguinness

src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs

@@ -1132,7 +1132,7 @@ protected virtual void GenerateCreateExtension(
                 .Append(DelimitIdentifier(extension.Version));
         }
 
-        builder.AppendLine(";");
+        builder.AppendLine(" CASCADE;");
     }
 
     #region Collation management

test/EFCore.PG.FunctionalTests/Migrations/MigrationsNpgsqlTest.cs

@@ -2688,7 +2688,7 @@ await Test(
                 Assert.Equal("public", citext.Schema);
             });
 
-        AssertSql("CREATE EXTENSION IF NOT EXISTS citext;");
+        AssertSql("CREATE EXTENSION IF NOT EXISTS citext CASCADE;");
     }
 
     [Fact]
@@ -2714,7 +2714,7 @@ IF NOT EXISTS(SELECT 1 FROM pg_namespace WHERE nspname = 'some_schema') THEN
                 END $EF$;
                 """,
             //
-            @"CREATE EXTENSION IF NOT EXISTS citext SCHEMA some_schema;");
+            @"CREATE EXTENSION IF NOT EXISTS citext SCHEMA some_schema CASCADE;");
     }
 
     #endregion