The current script service has a script compilation limit for a one
minute window. This is set to a small default value of 15. Instead of
increasing that default value, this commit introduces a new setting
that allows to configure a rate per time unit, so that the script service can deal with bursts better.
The new setting is named `script.max_compilations_rate`,
requires a nonnegative number and a positive time value.
The default is `75/5m`, which is equivalent to the existing 15 per minute.
* Add parent-join module
This change adds a new module named `parent-join`.
The goal of this module is to provide a replacement for the `_parent` field but as a first step this change only moves the `has_child`, `has_parent` queries and the `children` aggregation to this module.
These queries and aggregations are no longer in core but they are deployed by default as a module.
Relates #20257