pgsql: lwlock: Remove support for disowned lwlwocks

lwlock: Remove support for disowned lwlwocks

This reverts commit f8d7f29b3e81db59b95e4b5baaa6943178c89fd8, plus parts of
subsequent commits fixing a typo in a parameter name.

Support for disowned lwlocks was added for the benefit of AIO, to be able to
have content locks "owned" by the AIO subsystem. But as of commit fcb9c977aa5,
content locks do not use lwlocks anymore.

It does not seem particularly likely that we need this facility outside of the
AIO use-case, therefore remove the now unused functions.

I did choose to keep the comment added in the aforementioned commit about
lock->owner intentionally being left pointing to the last owner.

Reviewed-by: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Discussion: https://postgr.es/m/cj5mcjdpucvw4a54hehslr3ctukavrbnxltvuzzhqnimvpju5e@cy3g3mnsefwz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d40fd85187d06f7bd16fb4d0067bad0b1d248718

Modified Files
--------------
src/backend/storage/lmgr/lwlock.c | 71 ++++-----------------------------------
src/include/storage/lwlock.h | 2 --
2 files changed, 6 insertions(+), 67 deletions(-)