Rename *_isin to *_contains

This is an automatically generated commit, from the following perl script,
run with the options "-w -i -p".

  s/smartlist_string_num_isin/smartlist_contains_int_as_string/g;
  s/smartlist_string_isin((?:_case)?)/smartlist_contains_string$1/g;
  s/smartlist_digest_isin/smartlist_contains_digest/g;
  s/smartlist_isin/smartlist_contains/g;
  s/digestset_isin/digestset_contains/g;