[TSDB] Exclude index.block.write setting when creating rollup index (#88812)

PR #88565 modified the rollup action so that it copies all index settings from the source 
to the rollup index. However, the rollup action expilitly requires that the source index has
 the index.block.write: true.

Since the rollup index must be writeable when it is created, this PR excludes the index.block.write i
ndex setting when creating the rollup index.

The index.block.write index setting is explictly set to true at the end of the rollup action (step 4).

Author: csoulios

x-pack/plugin/rollup/src/main/java/org/elasticsearch/xpack/rollup/v2/TransportRollupAction.java

@@ -483,8 +483,10 @@ private IndexMetadata.Builder copyIndexMetadata(IndexMetadata sourceIndexMetadat
                 // the same rules with resize apply
                 continue;
             }
-            // do not override settings that have already been set in the rollup index
-            if (targetSettings.keys().contains(key)) {
+            // Do not override settings that have already been set in the rollup index.
+            // Also, we don't want to copy the `index.block.write` setting that we know
+            // it is set in the source index settings.
+            if (IndexMetadata.SETTING_BLOCKS_WRITE.equals(key) || targetSettings.keys().contains(key)) {
                 continue;
             }
             targetSettings.copy(key, sourceIndexMetadata.getSettings());

x-pack/plugin/rollup/src/test/java/org/elasticsearch/xpack/rollup/v2/RollupActionSingleNodeTests.java

@@ -302,7 +302,8 @@ public void testCopyIndexSettings() throws IOException {
         prepareSourceIndex(sourceIndex);
         rollup(sourceIndex, rollupIndex, config);
 
-        GetIndexResponse indexSettingsResp = client().admin().indices().prepareGetIndex().addIndices(rollupIndex).get();
+        GetIndexResponse indexSettingsResp = client().admin().indices().prepareGetIndex().addIndices(sourceIndex, rollupIndex).get();
+        assertRollupIndexSettings(sourceIndex, rollupIndex, indexSettingsResp);
         for (String key : settings.keySet()) {
             assertEquals(settings.get(key), indexSettingsResp.getSetting(rollupIndex, key));
         }