Allow `html_form_submit()` *without* submit button

[netique]

Some old ASPX sites provide forms without a submission button, and POST/GET requests are made when the form field changes. As I can see in rvest:::submission_find_submit(), when there is no button, HTTP request is based just on the fields, which is what I would expect. However, if there is completely unrelated button somewhere in the website, it gets selected and used as a part of the form. I would like to see something like html_form_submit(submit = NA) that completely avoids the button search quest. To see this in the wild, navigate to https://vysledky.cermat.cz/statistika/, where there is a cookie bar with a button that gets entangled with the form. I know I can simply remove the interfering button from the DOM, but I guess it would be a whole lot easier with the change in {rvest} API.