Stop the Sync process if mapping failed

[burhandodhy]

Description of the Change

This PR updates the put_mapping method to return the WP_ERROR object in case there is issue while doing the mapping. The main reason to doing this is so we can stop the sync if there is an error and also shows the error message in dashboard and WP CLI command

Closes #3204

How to test the Change

1. Add this filter to enforce the mapping fail

add_filter(
	'ep_config_mapping_request',
	function() {
		return new \WP_Error( 'test', 'This was forced to fail' );
	}
);

2. Run the sync from dashboard and make sure the sync stopped and the message is logged
3. Run put-mapping command and it should display the error message

Changelog Entry

Changed - put-mapping wpcli returns error message if mapping failed
Fixed - Stopped Sync if put mapping throws error.

Credits

Props @burhandodhy @felipeelia

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.