Setting/manifest entry to persistently enable "oldest dependencies preferred"

[mosteo]

While using the newest available releases is the usual package manager behavior, to automatically get the latest fixes and features, others advice a more conservative approach in which updates must be forced (the only notable case I know is go).

Alire has some building blocks ready for this, that can be used through --prefer-oldest in some commands (get, show, search), but having a setting (or manifest switch) would allow using the conservative approach consistently across a workspace or crate.

Notably, alr update and automatic updates after manual manifest edition will currently always try to solve for newest dependencies.