Restore previous implementation of foldable for TextEmbedding function.

Author: afoucret

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/inference/InferenceFunction.java

@@ -36,10 +36,4 @@ protected InferenceFunction(Source source, List<Expression> children) {
     public abstract TaskType taskType();
 
     public abstract PlanType withInferenceResolutionError(String inferenceId, String error);
-
-    @Override
-    public boolean foldable() {
-        // Inference functions are not foldable and need to be evaluated using an async inference call.
-        return false;
-    }
 }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/inference/TextEmbedding.java

@@ -91,6 +91,11 @@ public Expression inferenceId() {
         return inferenceId;
     }
 
+    @Override
+    public boolean foldable() {
+        return inferenceId.foldable() && inputText.foldable();
+    }
+
     @Override
     public DataType dataType() {
         return DataType.DENSE_VECTOR;