pgsql: Pass CAC as an argument to the backend process

Pass CAC as an argument to the backend process

We used to smuggle it to the child process in the Port struct, but it
seems better to pass it down as a separate argument. This paves the
way for the next commit, which moves the initialization of the Port
struct to the backend process, after forking.

Reviewed-by: Tristan Partin, Andres Freund
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/d162c3a73bf14416ff4012de6f01c3d825610f70

Modified Files
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src/backend/postmaster/postmaster.c | 44 +++++++++++++++++++++++++++----------
src/include/libpq/libpq-be.h | 12 ----------
2 files changed, 32 insertions(+), 24 deletions(-)