pgsql: Use atomics to avoid locking in InjectionPointRun()

Use atomics to avoid locking in InjectionPointRun()

This allows using injection points without having a PGPROC, like early
at backend startup, or in the postmaster.

The injection points facility is new in v17, so backpatch there.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Disussion: https://www.postgresql.org/message-id/4317a7f7-8d24-435e-9e49-29b72a3dc418@iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/86db52a5062a77c6ee533586be2cef8672a20c7d

Modified Files
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src/backend/utils/misc/injection_point.c | 404 +++++++++++++++++++++----------
src/tools/pgindent/typedefs.list         |   1 +
2 files changed, 281 insertions(+), 124 deletions(-)