Refine before-submit.sh: also run under c++20 and c++23 #4957

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4 warnings and 2 notices

😱 syntax:opentitan Expected failures 90, got 94 (will be an error once 4 more)

😱 lint:opentitan Expected failures 90, got 94 (will be an error once 4 more)

😱 preprocessor:basejump_stl Expected failures 642, got 643 (will be an error once 32 more)

No files were found with the provided path: verible-*.tar.gz. No artifacts will be uploaded.

🎉 Yay, reduced non-zero exit count 1135 -> 1122

🎉 Yay, reduced non-zero exit count 3067 -> 3029