build, treewide: enable -Wpessimizing-move warning

This warning prevents using std::move() where it can hurt
- on an unnamed temporary or a named automatic variable being
returned from a function. In both cases the value could be
constructed directly in its final destination, but std::move()
prevents it.

Fix the handful of cases (all trivial), and enable the warning.

Closes #8992

db/view/build_progress_virtual_reader.hh

@@ -143,7 +143,7 @@ class build_progress_virtual_reader {
                         _previous_clustering_key = ck;
                         mf = mutation_fragment(*_schema, _permit, clustering_row(
                                 std::move(ck),
-                                std::move(scylla_in_progress_row.tomb()),
+                                scylla_in_progress_row.tomb(),
                                 std::move(scylla_in_progress_row.marker()),
                                 std::move(legacy_in_progress_row)));
                     } else if (mf.is_range_tombstone()) {