Coerce Distribution.script_args to list

[Avasam]

This will allow any iterable to be passed as script_args for setup.
After this is merged, typeshed can be updated to reflect this change, which will allow https://github.com/jaraco/jaraco.office/pull/2/files#diff-bb91dce3f1ce94166001a97817fed8d6a6a56c6d7f95233cc28268aea7f05778R24 to pass.

If you don't want the coercion, then script_args should at least be typed as Sequence[str] and python/typeshed#13116 should be merged first.

I also noticed, I think there's no validation that script_args isn't a plain str

[jaraco]

This will allow any iterable to be passed as script_args for setup.

Is this the right approach, versus requiring a list and requiring consumers to construct lists? I do think Iterable is generally preferable, but if this value is a pass-through to get-opt, I'm kinda inclined to just align with what it expects. Nah, this approach seems fine.

I also noticed, I think there's no validation that script_args isn't a plain str

I'm fine with that. If the type system allows for "IterableNotStringOrBytesOrDict", that might make sense, but it's kinda gross, so let's just leave it open unless the type system has a solution for that ambiguity.

[Avasam]

if this value is a pass-through to get-opt, I'm kinda inclined to just align with what it expects.

getopt is slightly mistyped atm. It accepts more than just list. I need to improve my PR on that, but python/typeshed#13116