`IMPORT FOREIGN SCHEMA` doesn't add to metadata when use_citus_managed_tables is on

We add newly created tables to Citus metadata when `citus.use_citus_managed_tables` is set to `on`. See https://github.com/citusdata/citus/pull/5440

This works for foreign tables as well. (See https://github.com/citusdata/citus/pull/5461)

But Citus doesn't add foreign tables that are imported from a schema to metadata, probably because of the
```c
if (context == PROCESS_UTILITY_TOPLEVEL &&
```
check in `utility_hook.c`.