update: support updating to hidden cset if directaccess config is set
This patch adds support for updating to a hidden changeset without using
--hidden if `experimental.directacces=True` is set. The update command will
print out a warning when updating to a hidden changeset saying:
`updating to a hidden changeset <hash>`
The warning is also printed when directaccess is not used and --hidden is
passed which I think is good behaviour. Tests are added for the directaccess
part and updated output of tests which have case of updating to hidden cset
using `--hidden`.
Differential Revision: https://phab.mercurial-scm.org/D1762