pg_stat_statements: Track I/O timing for temporary file blocks

pg_stat_statements: Track I/O timing for temporary file blocks

This commit adds two new columns to pg_stat_statements, called
temp_blk_read_time and temp_blk_write_time.  Those columns respectively
show the time spent to read and write temporary file blocks on disk,
whose tracking has been added in efb0ef9.  This information is
available when track_io_timing is enabled, like blk_read_time and
blk_write_time.

pg_stat_statements is updated to version to 1.10 as an effect of the
newly-added columns.  Tests for the upgrade path 1.9->1.10 are added.

PGSS_FILE_HEADER is bumped for the new stats file format.

Author: Masahiko Sawada
Reviewed-by: Georgios Kokolatos, Melanie Plageman, Julien Rouhaud,
Ranier Vilela
Discussion: https://postgr.es/m/CAD21AoAJgotTeP83p6HiAGDhs_9Fw9pZ2J=_tYTsiO5Ob-V5GQ@mail.gmail.com