[FIX][IMP] various: unsudo mail/view controller and get_access_action

This is a backport of saas-13 commit a9bd9ab1.

mail/view controller is a generic controller that redirects the user to a
given view, depending on the record and the user. Users may be redirected
to the backend form view, or to a website view. This is done notably by
calling get_access_action method that gives the action to perform (act_window
or url).

Previously this method was called using SUPERUSER. However it was therefore
impossible to know who the user was. This method is now called using the
current user. Various overrides of get_access_action have been updated to
add some logic and access rights check directly in the method allowing
more fine-grain behavior of the access action.