test-runner: remove declaration of unused function

This function is not used anywhere
test-runner: add commit to benchmarks

Save current HEAD commit along with benchmark, so that we can
evaluate regression
test/benchmarks: update README

add commit field information
autotools: don't delete benchmarks logs

It's better to keep benchmarks so that we have more data for regressions
autotools: make lib-test-* noinst libraries

Libraries from these tests are not intended to be installable/installed

fix: https://github.com/mchalupa/wayland-integration-tests/issues/1