we should always qualify `format_to` with its namespace. otherwise
we'd have following failure when compiling with libstdc++ from GCC-13:
```
/home/kefu/dev/scylladb/compaction/table_state.hh:65:16: error: call to 'format_to' is ambiguous
return format_to(ctx.out(), "{}.{} compaction_group={}", s->ks_name(), s->cf_name(), t.get_group_id());
^~~~~~~~~
```
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#13760
113fb32019