pgsql: Refactor pg_stat_get_lock() to use a helper function

Refactor pg_stat_get_lock() to use a helper function

This commit extracts the tuple-building logic from pg_stat_get_lock()
into a new static helper pg_stat_lock_build_tuples(). This is in
preparation for a follow-up patch, to add support for backend-level lock
stats, which will reuse the same helper.

This change follows the pattern established by pg_stat_io_build_tuples()
for IO stats and pg_stat_wal_build_tuple() for WAL stats.

Author: Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>
Reviewed-by: Tatsuya Kawata <kawatatatsuya0913(at)gmail(dot)com>
Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Reviewed-by: Tristan Partin <tristan(at)partin(dot)io>
Reviewed-by: Rui Zhao <zhaorui126(at)gmail(dot)com>
Discussion: https://postgr.es/m/aiAzEY+cMQb/W8yu(at)bdtpg

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/dfe7d17e00665875639e905fa385231dacc57c4e

Modified Files
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src/backend/utils/adt/pgstatfuncs.c | 47 ++++++++++++++++++++++++-------------
1 file changed, 31 insertions(+), 16 deletions(-)