bpo-34866: Adding max_num_fields to cgi.FieldStorage (GH-9660)


Adding `max_num_fields` to `cgi.FieldStorage` to make DOS attacks harder by
limiting the number of `MiniFieldStorage` objects created by `FieldStorage`.
(cherry picked from commit 209144831b0a19715bda3bd72b14a3e6192d9cc1)

Co-authored-by: matthewbelisle-wf <matthew.belisle@workiva.com>
5 files changed