... or so I hope. The main observation was that we still have both
hash_vcpu_for_each() and hash_domain_for_each(), where the latter was
introduced in 2014/15 to replace the former. Only some eight years
later we can now complete this conversion. Everything else addresses
other things noticed along the road.

1: replace sh_reset_l3_up_pointers()
2: drop hash_vcpu_foreach()
3: rename hash_domain_foreach()
4: re-work 4-level SHADOW_FOREACH_L2E()

See individual patches for changes.

Jan