add support for named arguments for filter_var and filter_input

[pilif]

this fixes #10809

[kkmuffme]

@weirdan review & merge please

[weirdan]

@pilif Thanks!

[weirdan]

@kkmuffme please refrain from such comments

1. They are annoying. I receive all updates on all pull requests and issues, there's no need to add additional noise
2. You're not a boss of mine, don't tell me what to do
3. I'm not the only maintainer here
4. The others don't need to be bugged either
5. We're volunteers here and do the work in our spare time when we have the time and energy

Now there could be times when an old PR or an issue may need to be brought up, but that certainly wasn't the case here or on other PRs you pinged me recently.

[kkmuffme]

@weirdan sorry, I really didn't mean to - my comment here was in response to your comment on the referenced issue #10809 (comment)

I receive all updates on all pull requests and issues, there's no need to add additional noise
I'm not the only maintainer here

Thanks for letting me know - since the repo is set up in a way that doesn't allow requesting reviews and other repos (e.g. DefinitelyTyped) that work similar use a bot to @ ping relevant people, I didn't know that the maintainers get notified about all PRs anyway.
I assumed originally that marking a PR "Ready to review" (from draft) would be sufficient, but since there are lots of old/unmerged PRs that are non-draft status, I wasn't sure about that, which is why I @ you after changing the PR status from draft.