tolerance -> cdf_cutoff

[sbfnk]

Description

This PR closes #714.

Initial submission checklist

• [X] My PR is based on a package issue and I have explicitly linked it.
• [X] I have tested my changes locally (using devtools::test() and devtools::check()).
• [X] I have added or updated unit tests where necessary.
• [X] I have updated the documentation if required and rebuilt docs if yes (using devtools::document()).
• [X] I have followed the established coding standards (and checked using lintr::lint_package()).
• [X] I have ~added~ edited a news item linked to this PR. (as change to development version)

After the initial Pull Request

• [x] I have reviewed Checks for this PR and addressed any issues as far as I am able.

[sbfnk]

Testing this uncovered some other small required changes that have been added here.