vmalert expects string value for stats.seriesFetched, so it is impossible
switching to number without breaking compatibility with old vmalert releases :(
It is still unclear why stats.seriesFetched has string type in the first place...
- Expose stats.seriesFetched at `/api/v1/query_range` responses too
for the sake of consistency.
- Initialize QueryStats when it is needed and pass it to EvalConfig then.
This guarantees that the QueryStats is properly collected when the query
contains some subqueries.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/891
This commit also adds `"isPartial":{true|false}` field to `/api/v1/*` responses. `"isPartial":true` is set when the response
is based on a partial data because some of vmstorage nodes weren't available during query processing.
