Allow blob operations on stateless threadpools

This commit allows blob store operations to be performed on stateless
thread pools.

server/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java

@@ -1987,7 +1987,14 @@ public long getRestoreThrottleTimeInNanos() {
     }
 
     protected void assertSnapshotOrGenericThread() {
-        assert ThreadPool.assertCurrentThreadPool(ThreadPool.Names.SNAPSHOT, ThreadPool.Names.SNAPSHOT_META, ThreadPool.Names.GENERIC);
+        // The Stateless plugin adds custom thread pools for object store operations
+        assert ThreadPool.assertCurrentThreadPool(
+            ThreadPool.Names.SNAPSHOT,
+            ThreadPool.Names.SNAPSHOT_META,
+            ThreadPool.Names.GENERIC,
+            "stateless_shard",
+            "stateless_translog"
+        );
     }
 
     @Override