test/cluster/dtest: add ScyllaCluster.compact() method

Add compact() method to ScyllaCluster, delegating to
ScyllaNode.compact() on each running node. Accepts optional
keyspace and tables parameters to allow scoping compaction to
specific keyspaces/tables.

Also fix ScyllaNode.compact() to use list[str] for tables
parameter and extend() instead of +=, so that passing a single
table name as a string does not iterate over its characters.

test/cluster/dtest/ccmlib/scylla_cluster.py

@@ -227,6 +227,11 @@ class ScyllaCluster:
     def flush(self) -> None:
         self.nodetool("flush")
 
+    def compact(self, keyspace: str = "", tables: list[str] | None = None) -> None:
+        for node in self.nodelist():
+            if node.is_running():
+                node.compact(keyspace=keyspace, tables=tables)
+
     @staticmethod
     def debug(message: str) -> None:
         logger.debug(message)

test/cluster/dtest/ccmlib/scylla_node.py

@@ -647,11 +647,12 @@ class ScyllaNode:
             cmd.append(table)
         self.nodetool(" ".join(cmd), **kwargs)
 
-    def compact(self, keyspace: str = "", tables: str | None = ()) -> None:
+    def compact(self, keyspace: str = "", tables: list[str] | None = None) -> None:
         compact_cmd = ["compact"]
         if keyspace:
             compact_cmd.append(keyspace)
-        compact_cmd += tables
+        if tables:
+            compact_cmd.extend(tables)
         self.nodetool(" ".join(compact_cmd))
 
     def drain(self, block_on_log: bool = False) -> None: