pidstat: Add option -R to display priority and policy information

Processes' scheduling priority and policy information are no longer
displayed with context switches stats. Create a dedicated report
instead, which can be displayed using pidstat's new option -R.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>
pidstat: Update manual page

Document the pidstat's new option -R in manual page.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>