Move the base table migration classes outside CustomOrderTable directory

These classes are generic and don't depend on the custom orders table
functionality, so they are moved from src/Database/Migrations/CustomOrderTable
to just src/Database/Migrations.

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/PostMetaToOrderMetaMigrator.php

@@ -5,6 +5,8 @@
 
 namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
 
+use Automattic\WooCommerce\Database\Migrations\MetaToMetaTableMigrator;
+
 /**
  * Helper class to migrate records from the WordPress post meta table
  * to the custom orders meta table.

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/PostToOrderAddressTableMigrator.php

@@ -5,6 +5,8 @@
 
 namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
 
+use Automattic\WooCommerce\Database\Migrations\MetaToCustomTableMigrator;
+
 /**
  * Helper class to migrate records from the WordPress post table
  * to the custom order addresses table.

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/PostToOrderOpTableMigrator.php

@@ -5,6 +5,8 @@
 
 namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
 
+use Automattic\WooCommerce\Database\Migrations\MetaToCustomTableMigrator;
+
 /**
  * Helper class to migrate records from the WordPress post table
  * to the custom order operations table.

plugins/woocommerce/src/Database/Migrations/CustomOrderTable/PostToOrderTableMigrator.php

@@ -5,6 +5,8 @@
 
 namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
 
+use Automattic\WooCommerce\Database\Migrations\MetaToCustomTableMigrator;
+
 /**
  * Helper class to migrate records from the WordPress post table
  * to the custom order table (and only that table - PostsToOrdersMigrationController

plugins/woocommerce/src/Database/Migrations/MetaToCustomTableMigrator.php

@@ -3,9 +3,7 @@
  * Generic migration class to move any entity, entity_meta table combination to custom table.
  */
 
-namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
+namespace Automattic\WooCommerce\Database\Migrations;
-
-use Automattic\WooCommerce\Database\Migrations\MigrationHelper;
 
 /**
  * Base class for implementing migrations from the standard WordPress meta table

plugins/woocommerce/src/Database/Migrations/MetaToMetaTableMigrator.php

@@ -3,9 +3,7 @@
  * Generic Migration class to move any meta data associated to an entity, to a different meta table associated with a custom entity table.
  */
 
-namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
+namespace Automattic\WooCommerce\Database\Migrations;
-
-use Automattic\WooCommerce\Database\Migrations\MigrationHelper;
 
 /**
  * Base class for implementing migrations from the standard WordPress meta table

plugins/woocommerce/src/Database/Migrations/TableMigrator.php

@@ -3,7 +3,7 @@
  * Base class for all the WP posts to order table migrator.
  */
 
-namespace Automattic\WooCommerce\Database\Migrations\CustomOrderTable;
+namespace Automattic\WooCommerce\Database\Migrations;
 
 /**
  * Base class for implementing WP posts to order tables migrations handlers.