Fix SearchStatsTest

Use actual node in test instead of the first node in the array
More test cleanups
Fixed `has_parent` query and filter returning no results with multi level child docs.
Added a benchmark for parent/child queries while indexing at the same time.
report details if shard response has failed shards
Correct offsets in FVH also if stored field is used for highlighting

The SimpleFragemntsBuilder did not correct offsets if the used
analysis chais could produce broken offsets that could lead to
StringArrayIndexOutOfBounds Exceptions

Closes #3140
Wfst suggester prototype