Fix benchmarks

[adriendelsalle]

Description

Fix benchmarks by removing benchs already reimplemented in other files:

• benchmark_flow_routing.cpp covered by benchmark_single_flow_router.cpp and benchmark_multi_flow_router.cpp
• benchmark_pflood.cpp covered by benchmark_sink_resolver.cpp

[benbovy]

Thanks @adriendelsalle, good catch.

Both benchmark_flow_routing.cpp and benchmark_pflood.cpp are remnants of functions that have been either removed from public API or completely removed. Perhaps we can get rid of them (at least benchmark_pflood.cpp as I don't think it provides more than what is already benchmark_sink_resolver.cpp).

[adriendelsalle]

@benbovy my bad, I started fixing the benchs before seing they were already covered by other/newer benchs.. I just pushed the last commit deleting those 2 files