Store full path in _ignored when ignoring dynamic array field (elastic#136315)

Currently, when a dynamic array field trips `index.mapping.total_fields.
limit` and is ignored due to `index.mapping.total_fields.
ignore_dynamic_beyond_limit`, the leaf name is stored in _ignored.

This is inconsistent with single-valued fields where the full path is
stored in _ignored.

This PR updates the logic so that in both cases, the full path is stored.

Author: jordan-powers

docs/changelog/136315.yaml

@@ -0,0 +1,5 @@
+pr: 136315
+summary: Store full path in `_ignored` when ignoring dynamic array field
+area: Mapping
+type: bug
+issues: []

server/src/internalClusterTest/java/org/elasticsearch/index/mapper/DynamicMappingIT.java

@@ -382,6 +382,14 @@ public void testIgnoreDynamicBeyondLimitObjectMultiField() {
         });
     }
 
+    public void testIgnoreDynamicBeyondLimitObjectArrayField() {
+        indexIgnoreDynamicBeyond(2, orderedMap("a", orderedMap("b", 1, "c", List.of(2, 3, 4))), fields -> {
+            assertThat(fields.keySet(), equalTo(Set.of("a.b", "_ignored")));
+            assertThat(fields.get("a.b").getValues(), Matchers.contains(1L));
+            assertThat(fields.get("_ignored").getValues(), Matchers.contains("a.c"));
+        });
+    }
+
     public void testIgnoreDynamicBeyondLimitRuntimeFields() {
         indexIgnoreDynamicBeyond(1, orderedMap("field1", 1, "field2", List.of(1, 2)), Map.of("dynamic", "runtime"), fields -> {
             assertThat(fields.keySet(), equalTo(Set.of("field1", "_ignored")));

server/src/main/java/org/elasticsearch/index/mapper/DocumentParser.java

@@ -659,7 +659,7 @@ private static void parseArrayDynamic(DocumentParserContext context, String curr
                         throw new IllegalArgumentException("failed to parse field [" + currentFieldName + " ]", e);
                     }
                 }
-                context.addIgnoredField(currentFieldName);
+                context.addIgnoredField(context.path().pathAsText(currentFieldName));
                 return;
             }
             parseNonDynamicArray(context, objectMapperFromTemplate, currentFieldName, currentFieldName);