ESQL - full text functions verifier tests refactor (#128775)

Author: carlosdelest

x-pack/plugin/esql/qa/testFixtures/src/main/resources/mapping-full_text_search.json

@@ -0,0 +1,26 @@
+{
+  "properties": {
+    "id": {
+      "type": "integer"
+    },
+    "title": {
+      "type": "text"
+    },
+    "body": {
+      "type": "text"
+    },
+    "tags": {
+      "type": "keyword"
+    },
+    "category": {
+      "type": "integer"
+    },
+    "published_date": {
+      "type": "date"
+    },
+    "vector": {
+      "type": "dense_vector",
+      "similarity": "l2_norm"
+    }
+  }
+}

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/fulltext/FullTextFunction.java

@@ -204,23 +204,7 @@ private static void checkFullTextQueryFunctions(LogicalPlan plan, Failures failu
             checkCommandsBeforeExpression(
                 plan,
                 condition,
-                Match.class,
-                lp -> (lp instanceof Limit == false) && (lp instanceof Aggregate == false),
-                m -> "[" + m.functionName() + "] " + m.functionType(),
-                failures
-            );
-            checkCommandsBeforeExpression(
-                plan,
-                condition,
-                MultiMatch.class,
-                lp -> (lp instanceof Limit == false) && (lp instanceof Aggregate == false),
-                m -> "[" + m.functionName() + "] " + m.functionType(),
-                failures
-            );
-            checkCommandsBeforeExpression(
-                plan,
-                condition,
-                Term.class,
+                FullTextFunction.class,
                 lp -> (lp instanceof Limit == false) && (lp instanceof Aggregate == false),
                 m -> "[" + m.functionName() + "] " + m.functionType(),
                 failures

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/fulltext/MultiMatch.java

@@ -379,7 +379,7 @@ public String functionName() {
     private TypeResolution resolveFields() {
         return fields.stream()
             .map(
-                (Expression field) -> isNotNull(field, sourceText(), FIRST).and(
+                (Expression field) -> isNotNull(field, sourceText(), SECOND).and(
                     isType(
                         field,
                         FIELD_DATA_TYPES::contains,