pgsql: Mop-up for wait event naming issues.

Mop-up for wait event naming issues.

Synchronize the event names for parallel hash join waits with other
event names, by getting rid of the slashes and dropping "-ing"
suffixes. Rename ClogGroupUpdate to XactGroupUpdate, to match the
new SLRU name. Move the ProcSignalBarrier event to the IPC category;
it doesn't belong under IO.

Also a bit more wordsmithing in the wait event documentation tables.

Discussion: https://postgr.es/m/4505.1589640417@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3048898e73c75f54bb259323382e0e7f6368cb6f

Modified Files
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doc/src/sgml/monitoring.sgml | 128 ++++++++++++++++++++----------------
src/backend/access/transam/clog.c | 2 +-
src/backend/executor/nodeHash.c | 22 +++----
src/backend/executor/nodeHashjoin.c | 8 +--
src/backend/postmaster/pgstat.c | 72 ++++++++++----------
src/include/pgstat.h | 36 +++++-----
6 files changed, 142 insertions(+), 126 deletions(-)