pgsql: Track total number of WAL records, FPIs and bytes generated in t

Track total number of WAL records, FPIs and bytes generated in the cluster.

Commit 6b466bf5f2 allowed pg_stat_statements to track the number of
WAL records, full page images and bytes that each statement generated.
Similarly this commit allows us to track the cluster-wide WAL statistics
counters.

New columns wal_records, wal_fpi and wal_bytes are added into the
pg_stat_wal view, and reports the total number of WAL records,
full page images and bytes generated in the , respectively.

Author: Masahiro Ikeda
Reviewed-by: Amit Kapila, Movead Li, Kyotaro Horiguchi, Fujii Masao
Discussion: https://postgr.es/m/35ef960128b90bfae3b3fdf60a3a860f@oss.nttdata.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/01469241b2ff6f17fc0b3f20f01559145ffab29e

Modified Files
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doc/src/sgml/monitoring.sgml         | 27 +++++++++++++++++++++++++
src/backend/catalog/system_views.sql |  3 +++
src/backend/postmaster/pgstat.c      | 38 ++++++++++++++++++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c  | 27 ++++++++++++++++++++-----
src/include/catalog/pg_proc.dat      |  5 +++--
src/include/pgstat.h                 |  6 ++++++
src/test/regress/expected/rules.out  |  7 +++++--
7 files changed, 104 insertions(+), 9 deletions(-)