pgsql: Allow background workers to bypass datallowconn

Allow background workers to bypass datallowconn

THis adds a "flags" field to the BackgroundWorkerInitializeConnection()
and BackgroundWorkerInitializeConnectionByOid(). For now only one flag,
BGWORKER_BYPASS_ALLOWCONN, is defined, which allows the worker to ignore
datallowconn.

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/eed1ce72e1593d3e8b7461d7744808d4d6bf402b

Modified Files
--------------
contrib/pg_prewarm/autoprewarm.c | 2 +-
src/backend/access/transam/parallel.c | 3 ++-
src/backend/bootstrap/bootstrap.c | 2 +-
src/backend/postmaster/autovacuum.c | 4 ++--
src/backend/postmaster/postmaster.c | 8 ++++----
src/backend/replication/logical/launcher.c | 2 +-
src/backend/replication/logical/worker.c | 3 ++-
src/backend/tcop/postgres.c | 2 +-
src/backend/utils/init/postinit.c | 10 +++++-----
src/include/miscadmin.h | 2 +-
src/include/postmaster/bgworker.h | 7 +++++--
11 files changed, 25 insertions(+), 20 deletions(-)