MB-10199 add admin auth sharing process for view engine

Couchbase view engine needs to know admin auth information for
opening a connection to couchbase bucket and start UPR streams
for password protected buckets. Added a registered process with
an API `cb_auth_info:get` to obtain admin user and password for
couchbase server.

Change-Id: I032f5174041adad1d21c72108f6ead01f0c7aadb
Reviewed-on: http://review.couchbase.org/35041
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Sarath Lakshman <sarath@couchbase.com>