this magic field does not exist anymore with elasticsearch 6
use computed field which it is named `alltext` by convention

It's not used (and therefore not real-life-tested) anywhere
and current implementation is known to be partial and a bit
hard to maintain.

(closes #17071989)

[search_helpers] only use common and phrase searches, stop splitting up elements into multi_mach (canceled the common word stop work removal)

[search_helpers] has_child query added to should instead of replacing the bool query (combine results)