This commit adds back "id" as the key within a script to specify a
stored script (which with file scripts now gone is no longer ambiguous).
It also adds "source" as a replacement for "code". This is in an attempt
to normalize how scripts are specified across both put stored scripts and script usages, including search template requests. This also deprecates the old inline/stored keys.
This commit adds a new bg_count field to the REST response of
SignificantTerms aggregations. Similarly to the bg_count that already
exists in significant terms buckets, this new bg_count field is set at
the aggregation level and is populated with the superset size value.
Added missing CONSOLE scripts to documentation for sampler and diversified_sampler aggs.
Includes new StackOverflow index setup in build.gradle
Closes#22746
* Formatting tweaks
Ryan Ernst
Tanguy Leroux
markharwood
Pascal Borreli
Jason Tedor
Robert Muir
Colin Goodheart-Smithe