pgsql: Report progress of streaming base backup.

Report progress of streaming base backup.

This commit adds pg_stat_progress_basebackup view that reports
the progress while an application like pg_basebackup is taking
a base backup. This uses the progress reporting infrastructure
added by c16dc1aca5e0, adding support for streaming base backup.

Bump catversion.

Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi, Amit Langote, Sergei Kornilov
Discussion: https://postgr.es/m/9ed8b801-8215-1f3d-62d7-65bff53f6e94@oss.nttdata.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e65497df8f85ab9b9084c928ff69f384ea729b24

Modified Files
--------------
doc/src/sgml/monitoring.sgml | 163 ++++++++++++++++++++++++++++++++++-
doc/src/sgml/protocol.sgml | 2 +-
doc/src/sgml/ref/pg_basebackup.sgml | 16 ++++
src/backend/access/transam/xlog.c | 13 +++
src/backend/catalog/system_views.sql | 16 ++++
src/backend/replication/basebackup.c | 99 ++++++++++++++++++++-
src/backend/utils/adt/pgstatfuncs.c | 2 +
src/include/catalog/catversion.h | 2 +-
src/include/commands/progress.h | 14 +++
src/include/pgstat.h | 3 +-
src/test/regress/expected/rules.out | 15 ++++
11 files changed, 339 insertions(+), 6 deletions(-)