Product List: Extra CSS Classes needed

From a conversation with @jameskoster:

Couple of things I need for edit view when you have some time;
- Can we add a `product-list—editing` (or something similar) class to `product-list` ?
- Can we add a class to `product-list__list-cell` to indicate that it contains an input?

Start by locating the product-list markup and the product-list__list-cell component or template, then inspect how the edit view is rendered. Add the requested editing and input-indicator classes, and verify that they appear on the relevant elements in edit view without affecting the other product-list states.

Written by the indexing model from the issue text.