pgsql: Add GUC to log long wait times on recovery conflicts.

Add GUC to log long wait times on recovery conflicts.

This commit adds GUC log_recovery_conflict_waits that controls whether
a log message is produced when the startup process is waiting longer than
deadlock_timeout for recovery conflicts. This is useful in determining
if recovery conflicts prevent the recovery from applying WAL.

Note that currently a log message is produced only when recovery conflict
has not been resolved yet even after deadlock_timeout passes, i.e.,
only when the startup process is still waiting for recovery conflict
even after deadlock_timeout.

Author: Bertrand Drouvot, Masahiko Sawada
Reviewed-by: Alvaro Herrera, Kyotaro Horiguchi, Fujii Masao
Discussion: https://postgr.es/m/9a60178c-a853-1440-2cdc-c3af916cff59@amazon.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0650ff23038bc3eb8d8fd851744db837d921e285

Modified Files
--------------
doc/src/sgml/config.sgml                      |  22 +++
doc/src/sgml/high-availability.sgml           |   6 +
src/backend/storage/buffer/bufmgr.c           |  30 ++++
src/backend/storage/ipc/standby.c             | 199 ++++++++++++++++++++++----
src/backend/storage/lmgr/proc.c               |  48 ++++++-
src/backend/utils/misc/guc.c                  |  10 +-
src/backend/utils/misc/postgresql.conf.sample |   2 +
src/include/storage/standby.h                 |   5 +-
8 files changed, 292 insertions(+), 30 deletions(-)