Ensure all team members of an on-call policy have acceptable notification config

[WillDaSilva]

Is your feature request related to a problem? Please describe.
By default new OneUptime users don't have call/SMS notifications enabled. If one such user becomes the primary on-call, and OneUptime attempts to notify them, they may not receive the notification quickly enough.

Describe the solution you'd like
Visibility into the notification settings users in an on-call policy would allow us to ensure that everyone can and will receive call/SMS notifications if there is a high/critical severity incident, or a high severity alert.

As a bonus, it'd be nice if a OneUptime monitor could alert us if someone in the on-call policy does not have their notification settings set up in a way we desire, e.g. they're missing a verified phone number, or they don't have OneUptime configured to send them a phone call if a high severity incident/alert goes off.

Describe alternatives you've considered
A way for OneUptime project admins/owners to directly set the on-call notification settings for all member would be preferable, but more work to implement. In any case, you'd still need a way to ensure members have added & verified their phone number, so this issue would ideally be done before such a feature is implemented.