Allow admin override of notification and idle settings

[sandys]

Is your feature request related to a problem? Please describe.
In organizations where chatops is critical or central to the functioning, we have noticed misses because users go on silent mode accidentally and then end up missing critical messages.

Describe the solution you'd like
While we can go on reminding people, the only long term solution is for admins to be able to set notification and idle settings at an organization level

Describe alternatives you've considered
Reminding people.

Additional context
This was the single most important request that blocked many many users from migrating to Stride from Hipchat.
Additional context here
https://jira.atlassian.com/browse/STRIDE-17
https://jira.atlassian.com/browse/STRIDE-2411

this will also have implications on
RocketChat/Rocket.Chat#10976
#787
RocketChat/Rocket.Chat#6079
RocketChat/Rocket.Chat#11559
RocketChat/Rocket.Chat#11517