Possibly show blocked-notice-logextract or userpage-userdoesnotexist when editing a user page

Bug is just about blocked-notice-logextract, but the same EditPage code also deals with
userpage-userdoesnotexist so lets deal with that too while we're here as it's trivial.

Bug: 51454
Change-Id: Ic8a8f135c9f76f645c25a31d9432b5e2786dcfa0