Changing passwordless link role to one that has an enforced password fails badly

[pascalwengerter]

Steps to reproduce

1. Set password protection to true for read-only link shares
2. Create non-read-only link share without password, then change it to read-only via dropdown
3. See both error and success message on the UI

Expected behaviour

See a modal that asks you to add a password since the role you're trying to change the link into requires one

Notes

Will need quite some acceptance test fixes and also take into account #6961, which will make the need to check the same condition on link creation as well