pgsql: process startup: Centralize pgwin32_signal_initialize() calls.

process startup: Centralize pgwin32_signal_initialize() calls.

For one, the existing location lead to somewhat awkward code in main(). For
another, the new location is easier to understand anyway.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-By: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/20210802164124.ufo5buo4apl6yuvs@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/07bf37850991c68a7038fb06186bddfd64c72faf

Modified Files
--------------
src/backend/main/main.c             | 29 +++++++++--------------------
src/backend/postmaster/postmaster.c |  9 ---------
src/backend/utils/init/miscinit.c   | 19 ++++++++++++++++++-
3 files changed, 27 insertions(+), 30 deletions(-)