Add dead items memory usage to VACUUM (VERBOSE) and autovacuum logs.

Add dead items memory usage to VACUUM (VERBOSE) and autovacuum logs.

This commit adds the total memory allocated during vacuum, the number
of times the dead items storage was reset, and the configured memory
limit. This helps users understand how much memory VACUUM required,
and such information can be used to avoid multiple index scans.

Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAHza6qcPitBCkyiKJosDTt3bmxMvzZOTONoebwCkBZrr3rk65Q%40mail.gmail.com