Label /proc/misc

Label /proc/misc and allow access to untrusted_apps targeting older API
versions, as well as update_engine_common.

/proc/misc is used by some banking apps to try to detect if they are
running in an emulated environment.

TODO: Remove access to proc:file from update_engine_common after more
testing.

Bug: 35917228
Test: Device boots and no new denials.
Change-Id: If1b97a9c55a74cb74d1bb15137201ffb95b5bd75