Add time preferences for user [FE]
We'd like to make displayed times in GitLab more customizable:
Once these attributes are available, we should allow them to be set in the user profile and user preferences. UX needed:
Timezone: consider making this available as a dropdown in the user profile. See !999 (closed) for an example.
Time display preferences (12h/24h, absolute/relative): consider displaying in the profile section or in Preferences.
We should also implement these datetime modifications, as investigated in #56997 (closed).