Detect and fix visibility map corruption in more cases

Detect and fix visibility map corruption in more cases

Move VM corruption detection and repair into heap page pruning. This
allows VM repair during on-access pruning, not only during vacuum.

Also, expand corruption detection to cover pages marked all-visible that
contain dead tuples and tuples inserted or deleted by in-progress
transactions, rather than only all-visible pages with LP_DEAD items.

Pinning the correct VM page before on-access pruning is cheap when
compared to the cost of actually pruning. The vmbuffer is saved in the
scan descriptor, so a query should only need to pin each VM page once,
and a single VM page covers a large number of heap pages.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Discussion: https://postgr.es/m/bqc4kh5midfn44gnjiqez3bjqv4zogydguvdn446riw45jcf3y%404ez66il7ebvk