ESQL: Fix Max doubles bug with negatives and add tests for Max and Min (#110586)

`MAX()` currently doesn't work with doubles smaller than
`Double.MIN_VALUE` (Note that `Double.MIN_VALUE` returns the smallest
non-zero positive, not the smallest double).

This PR adds tests for Max and Min, and fixes the bug (Detected by the
tests).

Also, as the tests now generate the docs, replaced the old docs with the
generated ones, and updated the Max&Min examples.

Author: ivancea

docs/changelog/110586.yaml

@@ -0,0 +1,5 @@
+pr: 110586
+summary: "ESQL: Fix Max doubles bug with negatives and add tests for Max and Min"
+area: ES|QL
+type: bug
+issues: []

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

@@ -11,10 +11,10 @@ The <<esql-stats-by>> command supports these aggregate functions:
 * <<esql-avg>>
 * <<esql-agg-count>>
 * <<esql-agg-count-distinct>>
-* <<esql-agg-max>>
+* <<esql-max>>
 * <<esql-agg-median>>
 * <<esql-agg-median-absolute-deviation>>
-* <<esql-agg-min>>
+* <<esql-min>>
 * <<esql-agg-percentile>>
 * experimental:[] <<esql-agg-st-centroid>>
 * <<esql-agg-sum>>
@@ -25,14 +25,14 @@ The <<esql-stats-by>> command supports these aggregate functions:
 
 include::count.asciidoc[]
 include::count-distinct.asciidoc[]
-include::max.asciidoc[]
 include::median.asciidoc[]
 include::median-absolute-deviation.asciidoc[]
-include::min.asciidoc[]
 include::percentile.asciidoc[]
 include::st_centroid_agg.asciidoc[]
 include::sum.asciidoc[]
 include::layout/avg.asciidoc[]
+include::layout/max.asciidoc[]
+include::layout/min.asciidoc[]
 include::layout/top.asciidoc[]
 include::values.asciidoc[]
 include::weighted-avg.asciidoc[]

docs/reference/esql/functions/description/max.asciidoc

@@ -16,7 +16,7 @@
 class MaxDoubleAggregator {
 
     public static double init() {
-        return Double.MIN_VALUE;
+        return -Double.MAX_VALUE;
     }
 
     public static double combine(double current, double v) {

docs/reference/esql/functions/description/min.asciidoc

@@ -18,6 +18,7 @@
 import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
 import org.elasticsearch.xpack.esql.expression.SurrogateExpression;
+import org.elasticsearch.xpack.esql.expression.function.Example;
 import org.elasticsearch.xpack.esql.expression.function.FunctionInfo;
 import org.elasticsearch.xpack.esql.expression.function.Param;
 import org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvMax;
@@ -31,7 +32,16 @@ public class Max extends NumericAggregate implements SurrogateExpression {
     @FunctionInfo(
         returnType = { "double", "integer", "long", "date" },
         description = "The maximum value of a numeric field.",
-        isAggregation = true
+        isAggregation = true,
+        examples = {
+            @Example(file = "stats", tag = "max"),
+            @Example(
+                description = "The expression can use inline functions. For example, to calculate the maximum "
+                    + "over an average of a multivalued column, use `MV_AVG` to first average the "
+                    + "multiple values per row, and use the result with the `MAX` function",
+                file = "stats",
+                tag = "docsStatsMaxNestedExpression"
+            ) }
     )
     public Max(Source source, @Param(name = "number", type = { "double", "integer", "long", "date" }) Expression field) {
         super(source, field);