gh-114258: Refactor Argument Clinic function name parser

[erlend-aasland]

Refactor state_modulename_name() of the parsing state machine, by
adding helpers for the sections that deal with ...:

1. parsing the function name
2. normalizing the function kind
3. dealing with cloned functions
4. resolving return converters
5. adding the function to the DSL parser

• Issue: Reduce critical section boilerplate in type slot implementations #114258

[erlend-aasland]

(I'll fix the mypy errors later)

[erlend-aasland]

FTR, most of this PR is just shuffling lines around and wrapping them in more targeted scopes.

[sobolevn]

Quick review :)

[erlend-aasland]

I addressed your remarks in be244f2, @sobolevn :)

[sobolevn]

Did you reject #114930 (comment) or missed it? :)

Update: Ok, I see that it was partially implemented :)

[sobolevn]

Thanks! We can work on better error messages in the next PRs.

[erlend-aasland]

Thanks! We can work on better error messages in the next PRs.

Yeah, I think we should try to do an audit of all the fail(...) calls. Let's open an issue.

[erlend-aasland]

Thanks for the review, Nikita. I'll wait a day or two to give Alex a chance to chime in (since I already pinged him about this).

[erlend-aasland]

Thanks for the review, Nikita. I'll wait a day or two to give Alex a chance to chime in (since I already pinged him about this).

Landing this tomorrow afternoon (CET).