[red-knot] improve function/bound method type display (#17294)

## Summary

* Partial #17238
* Flyby from discord discussion - `todo_type!` now statically checks for
no parens in the message to avoid issues between debug & release build
tests

## Test Plan

many mdtests are changing

crates/red_knot_python_semantic/resources/mdtest/annotations/callable.md

@@ -289,7 +289,7 @@ def _(c: Callable[[int, Unpack[Ts]], int]):
 from typing import Callable
 
 def _(c: Callable[[int], int]):
-    reveal_type(c.__init__)  # revealed: Literal[__init__]
+    reveal_type(c.__init__)  # revealed: def __init__(self) -> None
     reveal_type(c.__class__)  # revealed: type
 
     # TODO: The member lookup for `Callable` uses `object` which does not have a `__call__`