Remove feature flag from influencing the serialisation (#119875)

When serialising the `IndicesOptions` we were using the helper method
`IndicesOptions#allowSelectors()` to retrieve the value of the flag
`allowSelector` from the `GatekeeperOptions`. 

This helper method is taking into consideration the failure store
feature flag to ensure we will not allow selectors unless the feature
flag is enabled:

```
public boolean allowSelectors() {
        return DataStream.isFailureStoreFeatureFlagEnabled() && gatekeeperOptions.allowSelectors();
    }
```

This was tripping this test. In this case we do not want the feature
flag to influence the serialsation of the object. We only want it to be
used during index name expression resolution.

Fixes: #119862 Fixes: #119861  Fixes: #119860 Fixes: #119859 Fixes:
#119822 Fixes: #119821 Fixes: #119820 Fixes: #119819

muted-tests.yml

@@ -245,30 +245,6 @@ tests:
 - class: org.elasticsearch.xpack.esql.optimizer.LocalPhysicalPlanOptimizerTests
   method: testSingleMatchOperatorFilterPushdownWithStringValues {default}
   issue: https://github.com/elastic/elasticsearch/issues/119721
-- class: org.elasticsearch.script.mustache.SearchTemplateRequestTests
-  method: testConcurrentSerialization
-  issue: https://github.com/elastic/elasticsearch/issues/119819
-- class: org.elasticsearch.script.mustache.SearchTemplateRequestTests
-  method: testEqualsAndHashcode
-  issue: https://github.com/elastic/elasticsearch/issues/119820
-- class: org.elasticsearch.script.mustache.SearchTemplateRequestTests
-  method: testConcurrentEquals
-  issue: https://github.com/elastic/elasticsearch/issues/119821
-- class: org.elasticsearch.script.mustache.SearchTemplateRequestTests
-  method: testSerialization
-  issue: https://github.com/elastic/elasticsearch/issues/119822
-- class: org.elasticsearch.index.rankeval.RankEvalRequestTests
-  method: testSerialization
-  issue: https://github.com/elastic/elasticsearch/issues/119859
-- class: org.elasticsearch.index.rankeval.RankEvalRequestTests
-  method: testEqualsAndHashcode
-  issue: https://github.com/elastic/elasticsearch/issues/119860
-- class: org.elasticsearch.index.rankeval.RankEvalRequestTests
-  method: testConcurrentSerialization
-  issue: https://github.com/elastic/elasticsearch/issues/119861
-- class: org.elasticsearch.index.rankeval.RankEvalRequestTests
-  method: testConcurrentEquals
-  issue: https://github.com/elastic/elasticsearch/issues/119862
 
 # Examples:
 #

server/src/main/java/org/elasticsearch/action/support/IndicesOptions.java

@@ -884,7 +884,8 @@ public void writeIndicesOptions(StreamOutput out) throws IOException {
         if (ignoreUnavailable()) {
             backwardsCompatibleOptions.add(Option.ALLOW_UNAVAILABLE_CONCRETE_TARGETS);
         }
-        if (allowSelectors()) {
+        // Until the feature flag is removed we access the field directly from the gatekeeper options.
+        if (gatekeeperOptions().allowSelectors()) {
             if (out.getTransportVersion()
                 .between(TransportVersions.V_8_14_0, TransportVersions.REPLACE_FAILURE_STORE_OPTIONS_WITH_SELECTOR_SYNTAX)) {
                 backwardsCompatibleOptions.add(Option.ALLOW_FAILURE_INDICES);
@@ -1464,7 +1465,8 @@ public String toString() {
             + ignoreAliases()
             + ", ignore_throttled="
             + ignoreThrottled()
-            + (DataStream.isFailureStoreFeatureFlagEnabled() ? ", allow_selectors=" + allowSelectors() : "")
+            // Until the feature flag is removed we access the field directly from the gatekeeper options.
+            + (DataStream.isFailureStoreFeatureFlagEnabled() ? ", allow_selectors=" + gatekeeperOptions().allowSelectors() : "")
             + ']';
     }
 }