Improve `SplitByIntervalMiddleware` middleware to take in consideration `query_store_after` flag.

[alanprot]

Is your feature request related to a problem? Please describe.

When querying multiple days we can see that the queries are split in away that the boundary query goes to both ingesters and store gateway forcing the querier to do extra work to merge the responses.

Describe the solution you'd like

The SplitByIntervalMiddleware could be a little bit smarter and slit the query in a way that none of the queriers would go to the ingesters and store gateways at the same time.