refactor and clean up pseudo_pext benchmark python code

[lukevalenty]

Lots of feedback to refactor the pseudo_pext benchmark code in #535, this issue is being filed to track it's completion.

[elbeno]

• the pseudo_pext benchmark code needs to be moved out of the test area and into a separate benchmarking area
• benchmarking targets shouldn't be part of the ALL target
• pseudo_pext.cpp uses a C++23 feature (static variable in constexpr function); either needs to be changed for C++20 or run only with appropriate toolchains
• move the python scripts to a better place, clean them up
• generate the tables with gen_map_data.py as part of the build; don't keep generated source in the repo
• pseudo_pext.cpp crashes clang-18; doesn't build with clang-17 or gcc-13 (what I've tried so far)
• benchmark tests run with a post build step; better to use the pattern in the CICD repo. (Using build events in CMake is perhaps a code smell? BEs can't have dependencies.)