This is actually reasonable for a groupBy or lexicographic topNs that is
being used to do a "COUNT DISTINCT" kind of query. No aggregators are
needed for that query, and including a dummy aggregator wastes 8 bytes
per row.
It's kind of silly for timeseries, but why not.
* docs: replace OR by AND inside topnquery docs about multi value dimensions
* docs: replace OR by AND inside groupby docs about multi value dimensions
- Add central doc for multi-value dimensions, with some content from other docs.
- Link to multi-value dimension doc from topN and groupBy docs.
- Fixes a broken link from dimensionspecs.md, which was presciently already
linking to this nonexistent doc.
- Resolve inconsistent naming in docs & code (sometimes "multi-valued", sometimes
"multi-value") in favor of "multi-value".