pgsql: Change the type of WalReceiverWaitStart wait event from Client t

Change the type of WalReceiverWaitStart wait event from Client to IPC.

Previously the type of this wait event was Client. But while this
wait event is being reported, walreceiver process is waiting for
the startup process to set initial data for streaming replication.
It's not waiting for any activity on a socket connected to a user
application or walsender. So this commit changes the type for
WalReceiverWaitStart wait event to IPC.

Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/cdacc27c-37ff-f1a4-20e2-ce19933abfcc@oss.nttdata.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1e3e8b51bda8ddd59984230f876f199c9ce3166a

Modified Files
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doc/src/sgml/monitoring.sgml    | 10 +++++-----
src/backend/postmaster/pgstat.c |  6 +++---
src/include/pgstat.h            |  2 +-
3 files changed, 9 insertions(+), 9 deletions(-)