There was a duplicate code to create TYPELIB from List<String>:
- In typelib() and mysql_prepare_create_table(), which was used to initialize
  table fields.
- create_typelib() and sp_prepare_create_field(), which was used to initialize
  SP variables.
create_typelib() was incomplete and didn't check for wrong SET values.

Fix:
- Moving the code from create_typelib() and mysql_prepare_create_field()
  to news methods Column_definition::create_interval_from_interval_list()
  and Column_definition::prepare_interval_field().
- Moving the code from calculate_interval_lengths() in sql_table.cc
  to a new method Column_definition::calculate_interval_lengths(), as it's now
  needed only in Column_definition::create_interval_from_interval_list()
- Reusing the new method Column_definition::prepare_interval_field() in both
  mysql_prepare_create_table() and sp_prepare_create_field(), instead of the
  old duplicate code pieces
- Removing global functions typelib() and create_typelib()

This patch also fixes:
MDEV-11155 Bad error message when creating a SET column with comma and non-ASCII characters
The problem was that ErrCongString() was called with a wrong "charset" parameter.