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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master

Details
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https://git.postgresql.org/pg/commitdiff/c558e6fd92ffeb85d5f52e32ccbcf8a5b5eb7bf3

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