Report visibility errors in both check and gather phases

Previously, errors that were found when splitting visibility rules were
only reported in the check phase and simply ignored during the gather
phase. That was because every visibility property that was processed in
the gather phase had already been checked in the check phase. However,
that is not strictly true as it has always been possible to add a
mutator between the check and gather phases that creates a module with
invalid visibility properties that will just be ignored. Fortunately,
that has not happened.

A follow up commit will add the capability to create modules after the
defaults have been applied which means the chances of invalid visibility
properties being ignored will increase.

This change makes both phases report any errors they find. It will not
have any impact on existing code as if any errors are reported in the
check phase then the build will exit before the gather phase. It will
prevent any invalid visibility errors from being ignored.

Bug: 155295806
Test: m nothing
Change-Id: I101fa6b03d2530b16e4394a9e466fead48be0ff0