pgsql: Report wait events for local shell commands like archive_command

Report wait events for local shell commands like archive_command.

This commit introduces new wait events for archive_command,
archive_cleanup_command, restore_command and recovery_end_command.

Author: Fujii Masao
Reviewed-by: Bharath Rupireddy, Michael Paquier
Discussion: https://postgr.es/m/4ca4f920-6b48-638d-08b2-93598356f5d3@oss.nttdata.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1b06d7bac901e5fd20bba597188bae2882bf954b

Modified Files
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doc/src/sgml/monitoring.sgml | 22 +++++++++++++++++++++-
src/backend/access/transam/xlog.c | 6 ++++--
src/backend/access/transam/xlogarchive.c | 9 ++++++++-
src/backend/postmaster/pgarch.c | 3 +++
src/backend/utils/activity/wait_event.c | 12 ++++++++++++
src/include/access/xlogarchive.h | 2 +-
src/include/utils/wait_event.h | 4 ++++
7 files changed, 53 insertions(+), 5 deletions(-)