pgsql: Drop the redundant "Lock" suffix from LWLock wait event names.

Drop the redundant "Lock" suffix from LWLock wait event names.

This was mostly confusing, especially since some wait events in
this class had the suffix and some did not.

While at it, stop exposing MainLWLockNames[] as a globally visible
name; any code using that directly is almost certainly wrong, as
its name has been misleading for some time.
(GetLWLockIdentifier() is what to use instead.)

Discussion: https://postgr.es/m/28683.1589405363@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/14a91010912632cae322b06fce0425faedcf7353

Modified Files
--------------
doc/src/sgml/monitoring.sgml | 88 ++++++++++++------------
src/backend/storage/lmgr/generate-lwlocknames.pl | 8 ++-
src/backend/storage/lmgr/lwlock.c | 5 +-
src/include/storage/lwlock.h | 1 -
4 files changed, 53 insertions(+), 49 deletions(-)