Adds a Num.restrictToInterval function

[KilianVounckx]

This PR is the result from this issue and this zulip thread.

[Anton-4]

We don't run expects tests for Num.roc yet. I need to do #6289 before we merge this.

[github-actions[bot]]

Thank you for your contribution! Sometimes PRs end up staying open for a long time without activity, which can make the list of open PRs get long and time-consuming to review. To keep things manageable for reviewers, this bot automatically closes PRs that haven’t had activity in 60 days. This PR hasn’t had activity in 30 days, so it will be automatically closed if there is no more activity in the next 30 days. Keep in mind that PRs marked Closed are not deleted, so no matter what, the PR will still be right here in the repo. You can always access it and reopen it anytime you like!