Allow filters to sort on invisible columns

New filter_get_sort_properties_array() API function adds a new
$p_visible_only parameter to determine if sorting should be restricted
to visible columns (default) or allowed on all columns.

Existing filter_get_visible_sort_properties_array() becomes a proxy for
the new function.

Add $visible_only property to BugFilterQuery class, initialized in
Constructor via $p_config parameter, defaulting to true. It is used in
the build_order_by() method in the filter_get_sort_properties_array()
call.

filter_get_bug_rows() gets a new $p_visible_only parameter, passed on
to BugFilterQuery's constructor.

Fixes 0033992