sstable_directory: Enlight deletion log replay

Garbage collection of sstables is scattered between two strages -- g.c.
per-se and the regular processing.

The former stage collects deletion logs and for each log found goes
ahead and deletes the full sstable with the standard sequence:

- move TOC -> TOC.tmp
- remove components
- remove TOC.tmp

The latter stage picks up partially unlinked sstables that didn't go via
atomic deletion with the log. This comes as

- collect all components
  - keep TOC's and TOC.tmp's in separate lists
  - attach other components to TOC/TOC.tmp by generation value
- for all TOC.tmp's get all attached components and remove them
- continue loading TOC's with attached components

Said that, replaying deletion log can be as light as just the first step
out of the above sequence -- just move TOC to TOC.tmp. After that the
regular processing would pick the remaining components and clean them

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>

sstables/sstable_directory.cc

@@ -639,7 +639,8 @@ future<> sstable_directory::filesystem_components_lister::replay_pending_delete_
         boost::split(basenames, all, boost::is_any_of("\n"), boost::token_compress_on);
         auto tocs = boost::copy_range<std::vector<sstring>>(basenames | boost::adaptors::filtered([] (auto&& basename) { return !basename.empty(); }));
         co_await parallel_for_each(tocs, [&sstdir] (const sstring& name) {
-            return remove_by_toc_name(sstdir + "/" + name);
+            // Only move TOC to TOC.tmp, the rest will be finished by regular process
+            return make_toc_temporary(sstdir + "/" + name).discard_result();
         });
         sstlog.debug("Replayed {}, removing", pending_delete_log);
         co_await remove_file(pending_delete_log.native());