Simplify Version string used for upgrade tests

(cherry picked from commit a5a0648)

Author: ldematte

.buildkite/scripts/run-pr-upgrade-tests.sh

@@ -27,7 +27,7 @@ echo "Running PR upgrade tests from $BUILDKITE_PULL_REQUEST_BASE_BRANCH [$BASE_C
 cat <<EOF | buildkite-agent pipeline upload
 steps:
     - label: pr-upgrade $BUILDKITE_PULL_REQUEST_BASE_BRANCH -> $BUILDKITE_BRANCH
-      command: .ci/scripts/run-gradle.sh -Dbwc.checkout.align=true -Dorg.elasticsearch.build.cache.push=true -Dignore.tests.seed -Dscan.capture-file-fingerprints -Dtests.bwc.main.version=${VERSION}-SNAPSHOT -Dtests.bwc.refspec.main=${BASE_COMMIT} bcUpgradeTest -Dtests.jvm.argline="-Des.serverless_transport=true"
+      command: .ci/scripts/run-gradle.sh -Dbwc.checkout.align=true -Dorg.elasticsearch.build.cache.push=true -Dignore.tests.seed -Dscan.capture-file-fingerprints -Dtests.bwc.main.version=${VERSION} -Dtests.bwc.refspec.main=${BASE_COMMIT} bcUpgradeTest -Dtests.jvm.argline="-Des.serverless_transport=true"
       timeout_in_minutes: 300
       agents:
         provider: gcp

server/src/main/java/org/elasticsearch/index/IndexVersions.java

@@ -173,6 +173,7 @@ private static Version parseUnchecked(String version) {
     public static final IndexVersion SEQ_NO_WITHOUT_POINTS = def(9_027_0_00, Version.LUCENE_10_2_1);
     public static final IndexVersion INDEX_INT_SORT_INT_TYPE = def(9_028_0_00, Version.LUCENE_10_2_1);
     public static final IndexVersion MAPPER_TEXT_MATCH_ONLY_MULTI_FIELDS_DEFAULT_NOT_STORED = def(9_029_0_00, Version.LUCENE_10_2_1);
+    public static final IndexVersion TEST_INDEX_VERSION_DO_NOT_MERGE = def(9_030_0_00, Version.LUCENE_10_2_1);
 
     /*
      * STOP! READ THIS FIRST! No, really,