Fix release build for mapper-extras (#81780)

`mapper-extras` runs a test that requires the `tsdb` feature flag and
was failing the release build because it didn't configure it.

modules/mapper-extras/build.gradle

@@ -5,6 +5,9 @@
  * in compliance with, at your election, the Elastic License 2.0 or the Server
  * Side Public License, v 1.
  */
+
+import org.elasticsearch.gradle.internal.info.BuildParams
+
 apply plugin: 'elasticsearch.internal-yaml-rest-test'
 apply plugin: 'elasticsearch.yaml-rest-compat-test'
 apply plugin: 'elasticsearch.internal-cluster-test'
@@ -19,3 +22,9 @@ restResources {
     include '_common', 'cluster', 'field_caps', 'nodes', 'indices', 'index', 'search', 'get'
   }
 }
+
+if (BuildParams.isSnapshotBuild() == false) {
+  tasks.named("test").configure {
+    systemProperty 'es.index_mode_feature_flag_registered', 'true'
+  }
+}

modules/mapper-extras/src/internalClusterTest/java/org/elasticsearch/index/mapper/MatchOnlyTextFieldMapperTests.java → modules/mapper-extras/src/test/java/org/elasticsearch/index/mapper/extras/MatchOnlyTextFieldMapperTests.java

@@ -6,7 +6,7 @@
  * Side Public License, v 1.
  */
 
-package org.elasticsearch.index.mapper;
+package org.elasticsearch.index.mapper.extras;
 
 import org.apache.lucene.analysis.CannedTokenStream;
 import org.apache.lucene.analysis.Token;
@@ -16,8 +16,13 @@ import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.IndexableField;
 import org.apache.lucene.index.IndexableFieldType;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.index.mapper.extras.MapperExtrasPlugin;
-import org.elasticsearch.index.mapper.extras.MatchOnlyTextFieldMapper;
+import org.elasticsearch.index.mapper.DocumentMapper;
+import org.elasticsearch.index.mapper.KeywordFieldMapper;
+import org.elasticsearch.index.mapper.MappedFieldType;
+import org.elasticsearch.index.mapper.MapperParsingException;
+import org.elasticsearch.index.mapper.MapperService;
+import org.elasticsearch.index.mapper.MapperTestCase;
+import org.elasticsearch.index.mapper.ParsedDocument;
 import org.elasticsearch.index.query.SearchExecutionContext;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.xcontent.XContentBuilder;