`clustering_key_columns()` returns a range view, and `front()` returns
the reference to its first element. so we cannot assume the availability
of this reference after the expression is evaluated. to address this
issue, let's capture the returned range by value, and keep the first
element by reference.
this also silences warning from GCC-13:
```
/home/kefu/dev/scylladb/db/schema_tables.cc:3654:30: error: possibly dangling reference to a temporary [-Werror=dangling-reference]
3654 | const column_definition& first_view_ck = v->clustering_key_columns().front();
| ^~~~~~~~~~~~~
/home/kefu/dev/scylladb/db/schema_tables.cc:3654:79: note: the temporary was destroyed at the end of the full expression ‘(& v)->view_ptr::operator->()->schema::clustering_key_columns().boost::iterator_range<__gnu_cxx::__normal_iterator<const column_definition*, std::vector<column_definition> > >::<anonymous>.boost::iterator_range_detail::iterator_range_base<__gnu_cxx::__normal_iterator<const column_definition*, std::vector<column_definition> >, boost::iterators::random_access_traversal_tag>::<anonymous>.boost::iterator_range_detail::iterator_range_base<__gnu_cxx::__normal_iterator<const column_definition*, std::vector<column_definition> >, boost::iterators::bidirectional_traversal_tag>::<anonymous>.boost::iterator_range_detail::iterator_range_base<__gnu_cxx::__normal_iterator<const column_definition*, std::vector<column_definition> >, boost::iterators::incrementable_traversal_tag>::front()’
3654 | const column_definition& first_view_ck = v->clustering_key_columns().front();
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
```
Fixes#13720
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#13721
135b4fd434