This is a follow-up to MDEV-18733. As part of that fix, we made
dict_check_sys_tables() skip tables that would be dropped by
row_mysql_drop_garbage_tables().

DICT_ERR_IGNORE_DROP: A new mode where the file should not be attempted
to be opened.

dict_load_tablespace(): Do not try to load the tablespace if
DICT_ERR_IGNORE_DROP has been specified.

row_mysql_drop_garbage_tables(): Pass the DICT_ERR_IGNORE_DROP mode.

fil_space_for_table_exists_in_mem(): Remove a parameter.
The only caller that passed print_error_if_does_not_exist=true
was row_drop_single_table_tablespace().