`citus_worker_stat_activity` does not show queries executed via local execution

Although this is sort of expected, let's keep track of it. `citus_worker_stat_activity` is used to show the queries that are executed on the shards on MX.

For example, if you do a multi-shard update `UPDATE test SET x = 100` on the workers, you'd see something like:
```SQL
select query from citus_worker_stat_activity;
-[ RECORD 1 ]-------------------------------------
query | UPDATE public.test_102036 test SET x = 100
-[ RECORD 2 ]-------------------------------------
query | UPDATE public.test_102033 test SET x = 100
-[ RECORD 3 ]-------------------------------------
query | COMMIT PREPARED 'citus_7_37254_3133_6'
-[ RECORD 4 ]-------------------------------------
query | UPDATE public.test_102039 test SET x = 100
-[ RECORD 5 ]-------------------------------------
query | UPDATE public.test_102037 test SET x = 100
-[ RECORD 6 ]-------------------------------------
query | UPDATE public.test_102038 test SET x = 100
-[ RECORD 7 ]-------------------------------------
query | UPDATE public.test_102034 test SET x = 100
```

However, the locally executed commands will not show up in the `citus_worker_stat_activity` as we currently do this per query session base, and local execution is done on the same session where the actual distributed query is running.