If the target user is deactivated, `Reactivate this user` will be
shown as one of the options in the small user profile popover, where
`Manage this user` would usually be.
We rename `show_manage_user_option` to `can_manage_user` because now
it will also be used as the common condition for whether the current
user has administrative permission to active or deactivate the target
user.
The implementation closely follows the existing deactivation modal.
Fixes#21428.
chat.zulip.org discussion:
design > reactivate user from user popover
yogesh sirsat