Select Filter Operators for Facets

We had a request for an improvement to the search facets. The request was to provide an option on the facet filter operator for Keywords so one could choose "AND" instead of "OR". Currently, the only alternative to "OR" is "NOT". Of course, there will be UI considerations to make this intuitive to users. However, as a first step, I would like to be able to set the operator to "AND" when selecting multiple keywords in the facets interface. Other facets should remain "OR". How might I do this?
We are using GN 4.2.5, so Elasticsearch is involved.

Start by tracing the search facets interface and the existing OR/NOT operator handling, then follow how facet selections are sent to Elasticsearch. Done means Keywords facets can use AND for multiple selections while other facets remain OR, with an intuitive UI choice.

Written by the indexing model from the issue text.