[IMP] mail: use xmlid_to_res_id instead of ref in remaining places of mail

As explained in previous commit we can use xmlid_to_res_id instead of ref()
which leads to some query gain. This commit update some other less important
places: when setting activities as done and in the composer. This lead to
a gain in tests involving activities and composer, including tracking
triggering a template. On community runbot this leads to a gain of about 1K
queries.