Cleanup file structure

bench/perf_monitoring/changesets.txt

bench/perf_monitoring/gemm.cpp

bench/perf_monitoring/gemm_common.h

bench/perf_monitoring/gemm_settings.txt

bench/perf_monitoring/gemm_square_settings.txt

bench/perf_monitoring/gemv.cpp

bench/perf_monitoring/gemv_common.h

bench/perf_monitoring/gemv_settings.txt

bench/perf_monitoring/gemv_square_settings.txt

bench/perf_monitoring/gemvt.cpp

bench/perf_monitoring/lazy_gemm.cpp

bench/perf_monitoring/lazy_gemm_settings.txt

bench/perf_monitoring/llt.cpp

bench/perf_monitoring/make_plot.sh

bench/perf_monitoring/resources/chart_footer.html

bench/perf_monitoring/resources/chart_header.html

bench/perf_monitoring/resources/footer.html

bench/perf_monitoring/resources/header.html

bench/perf_monitoring/resources/s1.js

bench/perf_monitoring/resources/s2.js