ESQL: Support ST_EXTENT_AGG (#117451)

This PR adds support for ST_EXTENT_AGG aggregation, i.e., computing a bounding box over a set of points/shapes (Cartesian or geo). Note the difference between this aggregation and the already implemented scalar function ST_EXTENT.

This isn't a very efficient implementation, and future PRs will attempt to read these extents directly from the doc values.
We currently always use longitude wrapping, i.e., we may wrap around the dateline for a smaller bounding box. Future PRs will let the user control this behavior.
Fixes #104659.

Author: GalLalouche

docs/changelog/117451.yaml

@@ -0,0 +1,6 @@
+pr: 117451
+summary: ST_EXTENT aggregation
+area: ES|QL
+type: feature
+issues:
+ - 104659

docs/reference/esql/functions/aggregation-functions.asciidoc

@@ -17,6 +17,7 @@ The <<esql-stats-by>> command supports these aggregate functions:
 * <<esql-min>>
 * <<esql-percentile>>
 * experimental:[] <<esql-st_centroid_agg>>
+* experimental:[] <<esql-st_extent_agg>>
 * <<esql-std_dev>>
 * <<esql-sum>>
 * <<esql-top>>
@@ -33,6 +34,7 @@ include::layout/median_absolute_deviation.asciidoc[]
 include::layout/min.asciidoc[]
 include::layout/percentile.asciidoc[]
 include::layout/st_centroid_agg.asciidoc[]
+include::layout/st_extent_agg.asciidoc[]
 include::layout/std_dev.asciidoc[]
 include::layout/sum.asciidoc[]
 include::layout/top.asciidoc[]