Disable N-2 BWC tests for non-snapshot builds (#119583)

The tests added in #119468 do not work when executed in the
`release-test` pipeline: at some point a 9.0 non-snapshot node tries to
join the 8.18.0-SNAPSHOT cluster which is impossible due to a missing
`esql.metrics_syntax` feature which is only declared in snapshot builds.

Additionaly, the tests rely on unrelease code in 8.x so they won't work
until 8.18.0 is released.

I don't know how we deal with such issues today, but I'd like to unmute
the tests so that they are executed on CI while being disabled in
`release-test`.

Releates #119550

Author: tlrx

muted-tests.yml

@@ -236,38 +236,14 @@ tests:
 - class: org.elasticsearch.smoketest.MlWithSecurityIT
   method: test {yaml=ml/sparse_vector_search/Test sparse_vector search with query vector and pruning config}
   issue: https://github.com/elastic/elasticsearch/issues/119548
-- class: org.elasticsearch.lucene.RollingUpgradeSearchableSnapshotIndexCompatibilityIT
-  method: testSearchableSnapshotUpgrade {p0=[9.0.0, 8.18.0, 8.18.0]}
-  issue: https://github.com/elastic/elasticsearch/issues/119549
-- class: org.elasticsearch.lucene.RollingUpgradeSearchableSnapshotIndexCompatibilityIT
-  method: testMountSearchableSnapshot {p0=[9.0.0, 8.18.0, 8.18.0]}
-  issue: https://github.com/elastic/elasticsearch/issues/119550
-- class: org.elasticsearch.lucene.RollingUpgradeSearchableSnapshotIndexCompatibilityIT
-  method: testMountSearchableSnapshot {p0=[9.0.0, 9.0.0, 8.18.0]}
-  issue: https://github.com/elastic/elasticsearch/issues/119551
 - class: org.elasticsearch.index.engine.LuceneSyntheticSourceChangesSnapshotTests
   method: testSkipNonRootOfNestedDocuments
   issue: https://github.com/elastic/elasticsearch/issues/119553
-- class: org.elasticsearch.lucene.RollingUpgradeSearchableSnapshotIndexCompatibilityIT
-  method: testSearchableSnapshotUpgrade {p0=[9.0.0, 9.0.0, 8.18.0]}
-  issue: https://github.com/elastic/elasticsearch/issues/119560
-- class: org.elasticsearch.lucene.RollingUpgradeSearchableSnapshotIndexCompatibilityIT
-  method: testMountSearchableSnapshot {p0=[9.0.0, 9.0.0, 9.0.0]}
-  issue: https://github.com/elastic/elasticsearch/issues/119561
-- class: org.elasticsearch.lucene.RollingUpgradeSearchableSnapshotIndexCompatibilityIT
-  method: testSearchableSnapshotUpgrade {p0=[9.0.0, 9.0.0, 9.0.0]}
-  issue: https://github.com/elastic/elasticsearch/issues/119562
 - class: org.elasticsearch.xpack.ml.integration.ForecastIT
   method: testOverflowToDisk
   issue: https://github.com/elastic/elasticsearch/issues/117740
 - class: org.elasticsearch.xpack.security.authc.ldap.MultiGroupMappingIT
   issue: https://github.com/elastic/elasticsearch/issues/119599
-- class: org.elasticsearch.lucene.FullClusterRestartSearchableSnapshotIndexCompatibilityIT
-  method: testSearchableSnapshotUpgrade {p0=8.18.0}
-  issue: https://github.com/elastic/elasticsearch/issues/119631
-- class: org.elasticsearch.lucene.FullClusterRestartSearchableSnapshotIndexCompatibilityIT
-  method: testSearchableSnapshotUpgrade {p0=9.0.0}
-  issue: https://github.com/elastic/elasticsearch/issues/119632
 - class: org.elasticsearch.search.profile.dfs.DfsProfilerIT
   method: testProfileDfs
   issue: https://github.com/elastic/elasticsearch/issues/119711

qa/lucene-index-compatibility/build.gradle

@@ -14,12 +14,13 @@ buildParams.bwcVersions.withLatestReadOnlyIndexCompatible { bwcVersion ->
   tasks.named("javaRestTest").configure {
     systemProperty("tests.minimum.index.compatible", bwcVersion)
     usesBwcDistribution(bwcVersion)
-    enabled = true
+
+    // Tests rely on unreleased code in 8.18 branch
+    enabled = buildParams.isSnapshotBuild()
   }
 }
 
 tasks.withType(Test).configureEach {
   // CI doesn't like it when there's multiple clusters running at once
   maxParallelForks = 1
 }
-