Improve support for Python arguments

[koesie10]

This improves support for Python arguments by doing two things:

• When there is a function definition like:

def foo(x, y)
  return x + y

It is possible to call the function as normal foo(1, 2), which works with Argument[0] and Argument[1]. However, it's also possible to call this like foo(1, y = 2) or foo(x = 1, y = 2), which doesn't work for those same values (since the function definition isn't always available). Therefore, this changes the generation of these arguments to Argument[0,x:] and Argument[1,y:].

• When there is a function definition like:

def foo(x, /, y)
  return x + y

It is not possible to call this like foo(x = 5, y = 2), only as foo(5, 2) or foo(5, y = 2). So, unlike above, we should ensure that these arguments are not modeled as both Argument[0] and Argument[x:], but only as Argument[0].

The CodeQL query will return x/,y as the parameter string for this function. When there are multiple positional-only arguments, each argument name will be suffixed by /.

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[charisk]

The changes seem reasonable based on what you've described in the PR description.

Do you think it's worth adding some unit tests around this functionality?

[koesie10]

Do you think it's worth adding some unit tests around this functionality?

Yes, good call. I'll add some unit tests in a follow-up PR.