Reduce queries in Inbox Panel. (https://github.com/woocommerce/woocommerce-admin/pull/3977)

* Notes panel: only request fields needed for render.

* Avoid retrieving post meta for WC_Admin_Note objects.

It's an ID collision anyhow.

plugins/woocommerce-admin/client/header/activity-panel/panels/inbox/index.js

@@ -126,6 +126,18 @@ export default compose(
 			orderby: 'date',
 			order: 'desc',
 			status: 'unactioned',
+			_fields: [
+				'id',
+				'name',
+				'title',
+				'content',
+				'type',
+				'icon',
+				'status',
+				'actions',
+				'date_created',
+				'date_created_gmt',
+			],
 		};
 
 		const notes = getNotes( inboxQuery );

plugins/woocommerce-admin/src/Notes/WC_Admin_Note.php

@@ -151,6 +151,18 @@ class WC_Admin_Note extends \WC_Data {
 	|
 	*/
 
+	/**
+	 * Returns all data for this object.
+	 *
+	 * Override \WC_Data::get_data() to avoid errantly including meta data
+	 * from ID collisions with the posts table.
+	 *
+	 * @return array
+	 */
+	public function get_data() {
+		return array_merge( array( 'id' => $this->get_id() ), $this->data );
+	}
+
 	/**
 	 * Get note name.
 	 *