pgsql: Add stats_reset to pg_stat_user_functions

Add stats_reset to pg_stat_user_functions

It is possible to call pg_stat_reset_single_function_counters() for a
single function, but the reset time was missing the system view showing
its statistics.  Like all the fields of pg_stat_user_functions, the GUC
track_functions needs to be enabled to show the statistics about
function executions.

Bump catalog version.
Bump PGSTAT_FILE_FORMAT_ID, as a result of the new field added to
PgStat_StatFuncEntry.

Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/aONjnsaJSx-nEdfU@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b71bae41a0cdda879db39d9946d2cc4af910bed1

Modified Files
--------------
doc/src/sgml/monitoring.sgml                 |  9 +++++++++
src/backend/catalog/system_views.sql         |  3 ++-
src/backend/utils/activity/pgstat.c          |  1 +
src/backend/utils/activity/pgstat_function.c |  6 ++++++
src/backend/utils/adt/pgstatfuncs.c          | 18 ++++++++++++++++++
src/include/catalog/catversion.h             |  2 +-
src/include/catalog/pg_proc.dat              |  4 ++++
src/include/pgstat.h                         |  3 ++-
src/include/utils/pgstat_internal.h          |  1 +
src/test/isolation/expected/stats.out        | 20 +++++++++++++++++++-
src/test/isolation/expected/stats_1.out      | 20 +++++++++++++++++++-
src/test/isolation/specs/stats.spec          |  8 ++++++--
src/test/regress/expected/rules.out          |  3 ++-
13 files changed, 90 insertions(+), 8 deletions(-)