The MySQL ACL system does not currently support granting stuff to public.
So the only currently possible fix is to make performance schema override
the ACL code and return that the tables are accessible to public.

Fixed by reverting parts of the fix for bug #14569746 pertaining to
PERFORMANCE_SCHEMA.SESSION_ACCOUNT_CONNECT_ATTR, namely re-introducing
the PFS_readonly_world_acl derived class and returning it into the tables
share.

Also used PFS_readonly_world_acl (and another derivate
of PFS_truncatable_world_acl) to ensure performance_schema.session_status,
performance_schema.global_status, performance_schema.session_variables and
performance_schema.global_variables are using the world readable derivates
too.
Test cases updated.