All CQL type implementations have a from_sstring(sstring_view) method.
The "sstring_view" type is just an historic alias for std::string_view,
so this patch switches to use the standard type as suggested in #4062,
and also renames these functions from_string_view() to emphesize they can
take any string view, and not necessarily a "sstring" as their old name
suggested.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
766ee56536