ESQL: Accept unsigned longs on MAX and MIN aggregations (#131694)

Solved #112006, but I'll change other uses of "representable" in another PR, so keeping it open.

- Fix aggregation tests to accept unsigned longs (They weren't correctly handling BigIntegers)
- Added unsigned long support for Max and Min (No new logics, reusing the existing Long aggregators)
- Test and docs

Author: ivancea

docs/changelog/131694.yaml

@@ -0,0 +1,5 @@
+pr: 131694
+summary: Accept unsigned longs on MAX and MIN aggregations
+area: ES|QL
+type: enhancement
+issues: []

docs/reference/query-languages/esql/_snippets/functions/types/max.md

@@ -5,6 +5,14 @@ l:long
 5
 ;
 
+maxOfUnsignedLong
+required_capability: agg_max_min_unsigned_long
+from ul_logs | stats ul = max(bytes_in);
+
+ul:ul
+18446744073709551615
+;
+
 maxOfInteger
 // tag::max[]
 FROM employees
@@ -18,6 +26,21 @@ MAX(languages):integer
 // end::max-result[]
 ;
 
+minOfLong
+from employees | stats l = min(languages.long);
+
+l:long
+1
+;
+
+minOfUnsignedLong
+required_capability: agg_max_min_unsigned_long
+from ul_logs | stats ul = min(bytes_in);
+
+ul:ul
+0
+;
+
 minOfInteger
 // tag::min[]
 FROM employees