Queries are not visible to the "system_views.queries" virtual table at the coordinator level

There appears to be a hole in the implementation of CASSANDRA-15241 where DebuggableTasks at the coordinator are not preserved through the creation of FutureTasks in TaskFactory. This means that QueriesTable can't see them when is asks SharedExecutorPool for running tasks. It should be possible to fix this in TaskFactory by making sure to propagate any RunnableDebuggableTask we encounter. We already do this in toExecute(), but it also needs to happen in the relevant toSubmit() method(s).