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_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2371432cd6b93415ef99e7ef35598f4f85436163

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