pgsql: Make levels 1-based in pg_log_backend_memory_contexts()

Make levels 1-based in pg_log_backend_memory_contexts()

Both pg_get_process_memory_contexts() and pg_backend_memory_contexts
have 1-based levels, whereas pg_log_backend_memory_contexts() was using
0-based levels. Align these.

This results in slightly saner behavior from MemoryContextStatsDetail()
in regards to the max_level. Previously it would stop at 1 level before
the maximum requested level rather than at that level.

Reported-by: Atsushi Torikoshi <torikoshia(at)oss(dot)nttdata(dot)com>
Author: Atsushi Torikoshi <torikoshia(at)oss(dot)nttdata(dot)com>
Author: David Rowley <drowleyml(at)gmail(dot)com
Reviewed-by: Melih Mutlu <m(dot)melihmutlu(at)gmail(dot)com>
Reviewed-by: Rahila Syed <rahilasyed90(at)gmail(dot)com>
Discussion: https://postgr.es/m/395ea5d4fe190480efa95bf533485c70@oss.nttdata.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d9e03864b6b4c7fe2988393c22e2355786c4c1f7

Modified Files
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src/backend/utils/mmgr/mcxt.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)