pgsql: Report progress of REINDEX operations

Report progress of REINDEX operations

This uses the same infrastructure that the CREATE INDEX progress
reporting uses.  Add a column to pg_stat_progress_create_index to
report the OID of the index being worked on.  This was not necessary
for CREATE INDEX, but it's useful for REINDEX.

Also edit the phase descriptions a bit to be more consistent with the
source code comments.

Discussion: https://www.postgresql.org/message-id/ef6a6757-c36a-9e81-123f-13b19e36b7d7%402ndquadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/03f9e5cba0ee1633af4abe734504df50af46fbd8

Modified Files
--------------
doc/src/sgml/monitoring.sgml         | 50 ++++++++++++++++++++++++++++--------
src/backend/catalog/index.c          | 10 ++++++++
src/backend/catalog/system_views.sql |  9 ++++---
src/backend/commands/indexcmds.c     | 41 +++++++++++++++++++++++++----
src/include/catalog/catversion.h     |  2 +-
src/include/commands/progress.h      |  3 +++
src/test/regress/expected/rules.out  |  9 ++++---
7 files changed, 101 insertions(+), 23 deletions(-)