simplebench: add img_bench_templater.py

simplebench: add img_bench_templater.py

Add simple grammar-parsing template benchmark. New tool consume test
template written in bash with some special grammar injections and
produces multiple tests, run them and finally print a performance
comparison table of different tests produced from one template.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210824101517.59802-2-vsementsov@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>