Feature request: Make runs private

[q-wertz]

Currently it is not possible to make the Run private, only the attached channel.

It would be nice, if one can set also the Run to private (maybe also from the Overview tab as creator of the Playbook) so only members of the team see the information inside and people who have it on auto-follow also do not see the content.

This is beneficial in many contexts where the Run itself contains sensitive data.