ESQL: Allow pruning columns added by InlineJoin (elastic#131204)

This updates `PruneColumns` rule to allow optimising away the columns added by `InlineJoin`, dropping unnecessary agg'ing.

Author: bpintea

docs/changelog/131204.yaml

@@ -0,0 +1,5 @@
+pr: 131204
+summary: Allow pruning columns added by `InlineJoin`
+area: ES|QL
+type: enhancement
+issues: []

x-pack/plugin/esql/qa/server/multi-clusters/src/javaRestTest/java/org/elasticsearch/xpack/esql/ccq/MultiClusterSpecIT.java

@@ -53,8 +53,7 @@
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.ENABLE_LOOKUP_JOIN_ON_REMOTE;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.FORK_V9;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.INLINESTATS;
-import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.INLINESTATS_V2;
-import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.INLINESTATS_V8;
+import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.INLINESTATS_V9;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_LOOKUP_V12;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_PLANNING_V1;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.METADATA_FIELDS_REMOTE_TEST;
@@ -150,9 +149,8 @@ protected void shouldSkipTest(String testName) throws IOException {
         Version oldVersion = Version.min(Clusters.localClusterVersion(), Clusters.remoteClusterVersion());
         assumeTrue("Test " + testName + " is skipped on " + oldVersion, isEnabled(testName, instructions, oldVersion));
         assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(INLINESTATS.capabilityName()));
-        assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(INLINESTATS_V2.capabilityName()));
         assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(JOIN_PLANNING_V1.capabilityName()));
-        assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(INLINESTATS_V8.capabilityName()));
+        assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(INLINESTATS_V9.capabilityName()));
         if (testCase.requiredCapabilities.contains(JOIN_LOOKUP_V12.capabilityName())) {
             assumeTrue("LOOKUP JOIN not yet supported in CCS", hasCapabilities(List.of(ENABLE_LOOKUP_JOIN_ON_REMOTE.capabilityName())));
         }