[red-knot] Recurse into the types of protocol members when normalizing a protocol's interface (#17808)
## Summary
Currently red-knot does not understand `Foo` and `Bar` here as being
equivalent:
```py
from typing import Protocol
class A: ...
class B: ...
class C: ...
class Foo(Protocol):
x: A | B | C
class Bar(Protocol):
x: B | A | C
```
Nor does it understand `A | B | Foo` as being equivalent to `Bar | B |
A`. This PR fixes that.
## Test Plan
new mdtest assertions added that fail on `main`
ruff
e6a798b9 - [red-knot] Recurse into the types of protocol members when normalizing a protocol's interface (#17808)
