[ty] Normalize recursive types using Any (#19003)

## Summary

This just replaces one temporary solution to recursive protocols (the
`SelfReference` mechanism) with another one (track seen types when
recursively descending in `normalize` and replace recursive references
with `Any`). But this temporary solution can handle mutually-recursive
types, not just self-referential ones, and it's sufficient for the
primer ecosystem and some other projects we are testing on to no longer
stack overflow.

The follow-up here will be to properly handle these self-references
instead of replacing them with `Any`.

We will also eventually need cycle detection on more recursive-descent
type transformations and tests.

## Test Plan

Existing tests (including recursive-protocol tests) and primer.

Added mdtest for mutually-recursive protocols that stack-overflowed
before this PR.

crates/ty_python_semantic/resources/mdtest/protocols.md

@@ -1729,6 +1729,21 @@ def _(r: Recursive):
     reveal_type(r.method(r).callable1(1).direct.t[1][1])  # revealed: Recursive
 ```
 
+### Mutually-recursive protocols
+
+```py
+from typing import Protocol
+from ty_extensions import is_equivalent_to, static_assert
+
+class Foo(Protocol):
+    x: "Bar"
+
+class Bar(Protocol):
+    x: Foo
+
+static_assert(is_equivalent_to(Foo, Bar))
+```
+
 ### Regression test: narrowing with self-referential protocols
 
 This snippet caused us to panic on an early version of the implementation for protocols.