Introduce parallel worker benchmark tools

Introduces a minimal scenario to bench eio. This is implemented as a tezt manual test.

It comes with a scripts allowing to generate nice graphs from profiling traces.

Manually testing the MR

Run the bench using TEZOS_PPX_PROFILER=t dune build tezt/manual_tests/eio_benchmarks && PROFILING="main->debug" PROFILING_BACKEND=txt _build/default/tezt/manual_tests/eio_benchmarks/test.exe 32

The graphs can be generated with: ./devtools/benchmarks-tools/profiler_viewer.sh /tmp/main_profiling.txt ./out.json out.vega

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR