Create category/product collection based on stock in 1 or more sources (and only from those sources)

### Description (*)
Currently it is impossible to create a category based on the products that have stock in 1 source. For sale or shipping purposes one would want to create a category (or product collection) that can be used that *only* holds the products that exist in the selected source. Layered nav would also have to follow the same stock limitations to build filters. Currently Magento cannot do this.

please add to Milestone 4: https://github.com/magento/inventory/wiki/MSI-Roadmap#mls4

### Expected behavior (*)
Product collections can be created based on a source. It was alreayd also asked in another context #2959 - apparently this is important.

### Benefits
Merchants can create categories or product collections based on 1 single source (like: these are all the products we have ready in London store, and these are all the products from source 4 (a sale source, full of returned items)

Start by reviewing the MSI Roadmap Milestone 4 entry and the related issue #2959. Define how product collections and layered navigation should be restricted to one or more selected sources, including the expected behavior for source stock. Done means the requested source-based categories or collections and matching filters are supported.

Written by the indexing model from the issue text.