The `IndexService#newQueryShardContext()` method creates a QueryShardContext on
shard `0`, with a `null` reader and that uses `System.currentTimeMillis()` to
resolve `now`. This may hide bugs, since the shard id is sometimes used for
query parsing (it is used to salt random score generation in `function_score`),
passing a `null` reader disables query rewriting and for some use-cases, it is
simply not ok to rely on the current timestamp (eg. percolation). So this pull
request removes this method and instead requires that all call sites provide
these parameters explicitly.
aa6cd93e0f