Track splatted variadic tuple shape during call matching

[alexander-beedie]

Summary

Overview

Calls to a function annotated *args: *tuple[*tuple[V, ...], S, S] were rejected, even when the arguments matched.

pyrefly already knows how to track positions through a splat, it just needed some additional wiring-up for CallArgPreEval::Star.

Solution

Give Star the same treatment Fixed already had; now carries the shape (prefix, middle, suffix) along with consumed, which has much the same role as Fixed's index. Note that it isn't exactly the same as a parameter consumes exactly one Fixed element, but a variadic parameter absorbs the remainder of a splat.

Fixes #4482.

Test Plan

All existing unit tests pass, and several new unit tests were added (including the one given in the original Issue, which has been added "as-is" 👍)

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D115423717. (Because this pull request was imported automatically, there will not be any future comments.)

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅