Filter by MSI source in Product Grid

### Description (*)
I would like a list of products that have been assigned to a specific source in the product grid.

### Expected behavior (*)
In the product grid, click on filter and have a source drop down box that is populated with all of the sources that exist.
Then select the source to filter and click apply filters.
### Result:
List of products that have been assigned to that particular source.

### Benefits
Help manage sources and stock for MSI.
Specifically, it would allow me to transfer all my stock from one source to another. As it would be a filter, it would also allow me to use other filters such as brand, size, name etc as well.
It would also allow me to assign and unassign sources more easily.

The issue does not name files or tests. Start by locating the product grid filter entry point and the existing MSI source and product-grid filtering code. Done means the filter offers existing sources, combines with other filters, and shows only products assigned to the selected source.

Written by the indexing model from the issue text.