[generate-ceval-switch] GH-98831: "Generate" the interpreter (GH-98830)

[qexat]

I noticed that some files in Tools/cases_generator/ have their code in the main() function, but others don't. This PR proposes to move lexer.py, parser.py, plexer.py and sparser.py main code to a main() function for consistency.

[qexat]

Sorry if the commit message does not fit Python's repo standards, I was not sure about what to put

[gvanrossum]

Thanks for the suggestion, but I'll leave this unmerged. There's a reason there are only two files that have a main() function -- those are the only ones that are meant as scripts (extract_cases.py and generate_cases.py). The others just have a little bit of hacky test code.

Also, note that it's uncommon to submit PRs to branches in my fork -- this is not our workflow (it may be different in some other projects). My branches are short-lived and not normally used for collaboration; if people have suggestions they tend to make them using GitHub's review UI against the PR (in this case, pythonGH-98830).

[qexat]

Understood. Sorry, I'm not very familiar with the workflow, next time I'll try to follow that.