pgsql: Refactor pgstat_prepare_io_time() with an input argument instead

Refactor pgstat_prepare_io_time() with an input argument instead of a GUC

Originally, this routine relied on track_io_timing to check if a time
interval for an I/O operation stored in pg_stat_io should be initialized
or not.  However, the addition of WAL statistics to pg_stat_io requires
that the initialization happens when track_wal_io_timing is enabled,
which is dependent on the code path where the I/O operation happens.

Author: Nazir Bilal Yavuz
Discussion: https://postgr.es/m/CAN55FZ3AiQ+ZMxUuXnBpd0Rrh1YhwJ5FudkHg=JU0P+-W8T4Vg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3c9d9acae0bc0cd2f905043cb1d581baec4622c4

Modified Files
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src/backend/storage/buffer/bufmgr.c    | 10 +++++-----
src/backend/storage/buffer/localbuf.c  |  4 ++--
src/backend/storage/smgr/md.c          |  4 ++--
src/backend/utils/activity/pgstat_io.c | 14 ++++++++++++--
src/include/pgstat.h                   |  2 +-
5 files changed, 22 insertions(+), 12 deletions(-)