Implement multi-range slice queries to retrieve requested properties only via a single Slice query

[porunov]

I haven't dive into this topic yet, but I was thinking that it might be really beneficial if we implement something like multi-slice queries. I.e. when we provide multiple ranges via a single Slice query.
If we can implement it, we would be able to retrieve all necessary properties / edges via a single Slice query instead of sending multiple slice queries OR instead of sending a single huge slice query which retrieves too many redundant data.
For example, if we support multi-slice queries we would be able to retrieve requested vertex properties of the next Gremlin query via a single multi-slice query: g.V(vertexId).properties("foo", "bar", "fooBar"). Right now we can retrieve those properties using separate slice queries (i.e. 3 queries in this case) or using a single slice query which retrieves ALL properties of the vertex.

This discussion diverges from this comment.

Separate discussion which attempts to optimize Slice queries is: #3811

I don't know if all storage backends can support this feature, but I guess we could have some feature flag (like we do with multiQuery and other storage related features).

cc @li-boxuan @FlorianHockmann in case you have any thoughts / ideas about it.