pgsql: Acquire ControlFileLock in relevant SQL functions.

Acquire ControlFileLock in relevant SQL functions.

Commit dc7d70ea added functions that read the control file, but didn't
acquire ControlFileLock.  With unlucky timing, file systems that have
weak interlocking like ext4 and ntfs could expose partially overwritten
contents, and the checksum would fail.

Back-patch to all supported releases.

Reviewed-by: David Steele <david@pgmasters.net>
Reviewed-by: Anton A. Melnikov <aamelnikov@inbox.ru>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/20221123014224.xisi44byq3cf5psi%40awork3.anarazel.de

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/606be8a35d9726b6c0468428b6262e58d9e308af

Modified Files
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src/backend/utils/misc/pg_controldata.c | 9 +++++++++
1 file changed, 9 insertions(+)