pgsql: Revert "graceful shutdown" changes for Windows, in back branches

Revert "graceful shutdown" changes for Windows, in back branches only.

This reverts commits 6051857fc and ed52c3707, but only in the back
branches. Further testing has shown that while those changes do fix
some things, they also break others; in particular, it looks like
walreceivers fail to detect walsender-initiated connection close
reliably if the walsender shuts down this way. We'll keep trying to
improve matters in HEAD, but it now seems unwise to push these changes
into stable releases.

Discussion: https://postgr.es/m/CA+hUKG+OeoETZQ=Qw5Ub5h3tmwQhBmDA=nuNO3KG=zWfUypFAw@mail.gmail.com

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/75674c7ec1b1607e7013b5cebcb22d9c8b4b2cb6

Modified Files
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src/backend/libpq/pqcomm.c | 29 +++++++----------------------
1 file changed, 7 insertions(+), 22 deletions(-)