CI: inclusion of the _index and _id for nested search breaks mixed cluster tests

[imotov]

Backport of #27201 to 6.2 seems to broke several tests that we ensuring that _index doesn't show up for nested hits. The issue is reproducible on 6.x branch with the following command line:

gradle :qa:mixed-cluster:v5.6.5-SNAPSHOT#mixedClusterTestRunner -Dtests.seed=E21365142E3CBA4E -Dtests.class=org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT -Dtests.security.manager=true -Dtests.locale=es-CU -Dtests.timezone=Antarctica/Macquarie

The following tests are currently failing:

org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=search.aggregation/200_top_hits_metric/top_hits aggregation with nested documents}
org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=search.inner_hits/10_basic/Nested inner hits}
org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=/10_parent_child/Parent/child inner hits}

The issue seems to be related to incorrectly determine if the test should be skipped in a mixed cluster.

[imotov]

I have muted these tests in 6.x, they don't let the intake job to pass.

[martijnvg]

I think problem is that in ESClientYamlSuiteTestCase#readVersionsFromCatNodes() instead of picking the lowest node version, the highest version is picked. I think that should be changed:

diff --git a/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/ESClientYamlSuiteTestCase.java b/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/ESClientYamlSuiteTestCase.java
index 92021dc5a7..09e2dfbca7 100644
--- a/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/ESClientYamlSuiteTestCase.java
+++ b/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/ESClientYamlSuiteTestCase.java
@@ -264,7 +264,7 @@ public abstract class ESClientYamlSuiteTestCase extends ESRestTestCase {
             }
             if (version == null) {
                 version = currentVersion;
-            } else if (version.onOrAfter(currentVersion)) {
+            } else if (version.onOrBefore(currentVersion)) {
                 version = currentVersion;
             }
         }

If this change is made then in case of a mixed cluster these tests that are now disabled run successfully, because then these tests will only if the cluster has been completed upgraded.

[martijnvg]

It turns out that the wrong version exclusion was used, I'll enable these test soon.