mutation_partition: verify row::append_cell() precondition

row::append_cell() has a precondition that the new cell column id needs
to be larger than that of any other already existing cell. If this
precondition is violated the row will end up in an invalid state. This
patch adds assertion to make sure we fail early in such cases.

(cherry picked from commit 060e3f8ac2)

mutation_partition.cc

@@ -1177,6 +1177,7 @@ row::apply_monotonically(const column_definition& column, atomic_cell_or_collect
 void
 row::append_cell(column_id id, atomic_cell_or_collection value) {
     if (_type == storage_type::vector && id < max_vector_size) {
+        assert(_storage.vector.v.size() <= id);
         _storage.vector.v.resize(id);
         _storage.vector.v.emplace_back(cell_and_hash{std::move(value), cell_hash_opt()});
         _storage.vector.present.set(id);