Add support for pg_stat_reset_slru without argument

Add support for pg_stat_reset_slru without argument

pg_stat_reset_slru currently requires an input argument, either:
- NULL to reset the SLRU counters of everything.
- A specific value to reset a single SLRU cache.

This commit adds support for a new pattern: pg_stat_reset_slru without
any argument works the same way as pg_stat_reset_slru(NULL), relying on
a DEFAULT in the function definition to handle this case.  This makes
the function more consistent with 23c8c0c8f472.

Bump catalog version.

Author: Bharath Rupireddy
Reviewed-by: Atsushi Torikoshi
Discussion: https://postgr.es/m/CALj2ACW1VizYg01EeH_cA-7qA+4NzWVAoZ5Lw9_XYO1RRHAZbA@mail.gmail.com