[ES|QL] Support for First/Last (#137408) (#138390)

- Skip vector optimization for block arguments when grouping, to prevent grouping aggs from executing the no-op path.
- This path will be enabled back once an actual implementation is in place.

Author: mouhc1ne

x-pack/plugin/esql/compute/gen/src/main/java/org/elasticsearch/compute/gen/GroupingAggregatorImplementer.java

@@ -335,7 +335,7 @@ private MethodSpec prepareProcessRawInputPage() {
             + aggParams.stream().map(arg -> arg.blockName()).collect(joining(", "))
             + ")";
 
-        if (allArgumentsSupportVectors) {
+        if (allArgumentsSupportVectors && hasOnlyBlockArguments == false) {
 
             for (Argument a : aggParams) {
                 builder.addStatement(