Allow to configure the source entity of the submission

Problem/Motivation

Recently, the module was updated so that the source entity for webform submissions is now the order instead of the node to which the form is attached. Previously, users could view webform submissions for a node by accessing the Results tab on that node's page.

With this update, however, submissions are now tied to the order rather than the node, meaning they will no longer appear under the Results tab on the node page. This affects forms that use the Commerce Webform Order handler.

This update have also affected tokens. For example, [webform_submission:node:title] used to be the Node title of which the webform is attached to. With the update, it is now the Order number. There is no way to access the Node title to use in the webform confirmation emails.

Steps to reproduce

1. Create a content type with an entity reference field for webforms
2. Create a webform with the commerce webform order handler
3. Create a new content using the content type you created. Reference the webform you just created in this content
4. Complete the form
5. Go back to the new content, click on the Results tab on the top of the page. The webform submission does not show. But if you go to Structure > Webform > find the webform > Results, the submission is shown there