The formatted_sstables_list is auxiliary class that collects a bunch of
sstables::to_string(shared_sstable)-generated strings. One of bad side
effects of this helper is that it allocates memory for the vector of
strings.
This patch achieves the same goal with the help of fmt::join() equipped
with transformed boost adaptor.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closesscylladb/scylladb#18160