[ty] Add cycle handling for unpacking targets (#18078)

## Summary

This PR adds cycle handling for `infer_unpack_types` based on the
analysis in astral-sh/ty#364.

Fixes: astral-sh/ty#364

## Test Plan

Add a cycle handling test for unpacking in `cycle.md`

crates/ty_python_semantic/resources/mdtest/cycle.md

@@ -13,3 +13,21 @@ def f(x: f):
 
 reveal_type(f)  # revealed: def f(x: Unknown) -> Unknown
 ```
+
+## Unpacking
+
+See: <https://github.com/astral-sh/ty/issues/364>
+
+```py
+class Point:
+    def __init__(self, x: int = 0, y: int = 0) -> None:
+        self.x = x
+        self.y = y
+
+    def replace_with(self, other: "Point") -> None:
+        self.x, self.y = other.x, other.y
+
+p = Point()
+reveal_type(p.x)  # revealed: Unknown | int
+reveal_type(p.y)  # revealed: Unknown | int
+```