[ES|QL] Update supported functions (#173835)

## Summary

Adds `least` and `to_cartesianpoint` functions support in ES|QL.

<img width="661" alt="Screenshot 2023-12-21 at 14 58 36"
src="e035f3cf-9776-41bd-8143-2292e7c3a459">
<img width="596" alt="Screenshot 2023-12-21 at 14 58 29"
src="53ee3fad-5394-4e8b-8e52-cfaa5f92750a">

packages/kbn-monaco/src/esql/antlr/esql_lexer.g4

@@ -168,6 +168,7 @@ MATH_FUNCTION
     | C O N C A T
     | C O A L E S C E
     | G R E A T E S T
+    | L E A S T
     | L E F T
     | N O W
     | R I G H T
@@ -209,6 +210,7 @@ MATH_FUNCTION
     | T O UNDERSCORE V E R S I O N
     | T O UNDERSCORE U N S I G N E D UNDERSCORE L O N G
     | T O UNDERSCORE G E O P O I N T
+    | T O UNDERSCORE C A R T E S I A N P O I N T
     ;
 
 UNARY_FUNCTION