pgsql: Refactor how InitProcess is called

Refactor how InitProcess is called

The order of process initialization steps is now more consistent
between !EXEC_BACKEND and EXEC_BACKEND modes. InitProcess() is called
at the same place in either mode. We can now also move the
AttachSharedMemoryStructs() call into InitProcess() itself. This
reduces the number of "#ifdef EXEC_BACKEND" blocks.

Reviewed-by: Tristan Partin, Andres Freund, Alexander Lakhin
Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/fd5e8b440dfd633be74e3dd3382d4a9038dba24f

Modified Files
--------------
src/backend/postmaster/autovacuum.c | 16 ++++---------
src/backend/postmaster/auxprocess.c |  5 +----
src/backend/postmaster/bgworker.c   |  8 ++-----
src/backend/postmaster/postmaster.c | 45 +++++--------------------------------
src/backend/storage/lmgr/proc.c     | 24 ++++++++++++++++++--
5 files changed, 35 insertions(+), 63 deletions(-)