See MONGOSH-1893 for motivation – this is something that's a bit more narrowly scoped but also more actionable. We already disable Node.js warnings via process.removeAllListeners('warning'); for the compiled binary, and should be able to just always do that in quiet mode. For warnings originating from mongosh, we'll probably need to pass the quiet flag into the ShellInstanceState so that printDeprecationWarning can adjust its behavior accordingly.