ESQL: Fix DEBUG log of filter (#116086)

This fixes the `DEBUG` level logging of `WHERE`. Previously it was using
a `ThrowingDriverContext` to render the description - but this throwing
context will, well, throw if you touch it. This removes the
`ThrowingDriverContext` entirely because it's never the right thing to
use - instead we just use the `toString` of the factories. That works
fine because we made sure that the factories had a nice `toString`.

Closes #116055

Author: nik9000

docs/changelog/116086.yaml

@@ -0,0 +1,6 @@
+pr: 116086
+summary: "ESQL: Fix DEBUG log of filter"
+area: ES|QL
+type: bug
+issues:
+ - 116055

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/FilterOperator.java

@@ -28,7 +28,7 @@ public Operator get(DriverContext driverContext) {
 
         @Override
         public String describe() {
-            return "FilterOperator[evaluator=" + evaluatorSupplier.get(new ThrowingDriverContext()) + "]";
+            return "FilterOperator[evaluator=" + evaluatorSupplier + "]";
         }
     }