pgsql: Add contrib/pg_walinspect.

Add contrib/pg_walinspect.

Provides similar functionality to pg_waldump, but from a SQL interface
rather than a separate utility.

Author: Bharath Rupireddy
Reviewed-by: Greg Stark, Kyotaro Horiguchi, Andres Freund, Ashutosh Sharma, Nitin Jadhav, RKN Sai Krishna
Discussion: https://postgr.es/m/CALj2ACUGUYXsEQdKhEdsBzhGEyF3xggvLdD8C0VT72TNEfOiog%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2258e76f90bf0254504644df0515cddc0c0a87f9

Modified Files
--------------
contrib/Makefile | 1 +
contrib/pg_walinspect/.gitignore | 4 +
contrib/pg_walinspect/Makefile | 23 +
contrib/pg_walinspect/expected/pg_walinspect.out | 165 ++++++
contrib/pg_walinspect/pg_walinspect--1.0.sql | 118 +++++
contrib/pg_walinspect/pg_walinspect.c | 629 +++++++++++++++++++++++
contrib/pg_walinspect/pg_walinspect.control | 5 +
contrib/pg_walinspect/sql/pg_walinspect.sql | 120 +++++
doc/src/sgml/contrib.sgml | 1 +
doc/src/sgml/filelist.sgml | 1 +
doc/src/sgml/func.sgml | 2 +-
doc/src/sgml/pgwalinspect.sgml | 275 ++++++++++
src/backend/access/rmgrdesc/xlogdesc.c | 130 +++++
src/backend/access/transam/Makefile | 1 +
src/backend/access/transam/xlogreader.c | 9 -
src/backend/access/transam/xlogstats.c | 93 ++++
src/backend/access/transam/xlogutils.c | 33 ++
src/bin/pg_waldump/.gitignore | 1 +
src/bin/pg_waldump/Makefile | 8 +-
src/bin/pg_waldump/pg_waldump.c | 206 +-------
src/include/access/xlog.h | 2 +-
src/include/access/xlog_internal.h | 6 +-
src/include/access/xlogreader.h | 2 -
src/include/access/xlogstats.h | 40 ++
src/include/access/xlogutils.h | 4 +
25 files changed, 1675 insertions(+), 204 deletions(-)