pgsql: Rename PGPROC->vacuumFlags to statusFlags

Rename PGPROC->vacuumFlags to statusFlags

With more flags associated to a PGPROC entry that are not related to
vacuum (currently existing or planned), the name "statusFlags" describes
its purpose better.

(The same is done to the mirroring PROC_HDR->vacuumFlags.)

No functional changes in this commit.

This was suggested first by Hari Babu Kommi in [1] and then by Michael
Paquier at [2].

[1] https://postgr.es/m/CAJrrPGcsDC-oy1AhqH0JkXYa0Z2AgbuXzHPpByLoBGMxfOZMEQ@mail.gmail.com
[2] https://postgr.es/m/20200820060929.GB3730@paquier.xyz

Author: Dmitry Dolgov <9erthalion6@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20201116182446.qcg3o6szo2zookyr@localhost

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/cd9c1b3e197a9b53b840dcc87eb41b04d601a5f9

Modified Files
--------------
src/backend/access/transam/twophase.c     |  2 +-
src/backend/commands/vacuum.c             |  6 ++--
src/backend/postmaster/autovacuum.c       |  6 ++--
src/backend/replication/logical/logical.c |  4 +--
src/backend/replication/slot.c            |  4 +--
src/backend/storage/ipc/procarray.c       | 54 +++++++++++++++----------------
src/backend/storage/lmgr/deadlock.c       |  4 +--
src/backend/storage/lmgr/proc.c           | 20 ++++++------
src/include/storage/proc.h                | 13 ++++----
9 files changed, 57 insertions(+), 56 deletions(-)