compaction: Allow reshape to be aborted

Now reshape can be aborted on either boot or refresh.

The workflow is:
    1) reshape starts
    2) user notices it's taking too long
    3) nodetool stop RESHAPE

the good thing is that completed reshape work isn't lost, allowing
table to enjoy the benefits of all reshaping done up to the abortion
point.

Fixes #7738.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>

compaction/compaction_manager.cc

@@ -317,6 +317,7 @@ future<> compaction_manager::run_custom_job(column_family* cf, sstables::compact
             f.get();
         } catch (sstables::compaction_stop_exception& e) {
             cmlog.info("{} was abruptly stopped, reason: {}", task->type, e.what());
+            throw;
         } catch (...) {
             cmlog.error("{} failed: {}", task->type, std::current_exception());
             throw;

sstables/sstable_directory.cc

@@ -362,7 +362,13 @@ future<uint64_t> sstable_directory::reshape(compaction_manager& cm, table& table
                         return collect_output_sstables_from_reshaping(std::move(new_sstables));
                     });
                 });
-            }).then([] {
+            }).then_wrapped([&table] (future<> f) {
+                try {
+                    f.get();
+                } catch (sstables::compaction_stop_exception& e) {
+                    dirlog.info("Table {}.{} with compaction strategy {} had reshape successfully aborted.", table.schema()->ks_name(), table.schema()->cf_name(), table.get_compaction_strategy().name());
+                    return make_ready_future<stop_iteration>(stop_iteration::yes);
+                }
                 return make_ready_future<stop_iteration>(stop_iteration::no);
             });
         }).then([&reshaped_size] {