Display Union of Literals as a Literal

[Glyphack]

Summary

Resolves #14988

Display union of Literals like other type checkers do.

With this change we lose the sorting behavior. We need to make sure types show as the order they appear so tests are not flaky. I’m not sure if we want to keep the sorting on integers if the goal is to show literal unions like other type checkers. Mypy does not sort int literals in a union:

https://mypy-play.net/?mypy=latest&python=3.12&gist=51ad03b153bfca3b940d5084345e230f

Test Plan

I was not sure about this one. Other type checkers do not support this.

def _(flag: bool, flag2: bool):
    if flag:
        f = 1
    elif flag2:
        f = "foo"
    else:
        def f() -> int:
            return 1
    # error: "Object of type `Literal[1, "foo", f]` is not callable (due to union elements Literal[1], Literal["foo"])"
    # revealed: Unknown | int
    reveal_type(f())

https://pyright-play.net/?code=GYJw9gtgBALgngBwJYDsDmUkQWEMoAySMApiAIYA2AUNQCYnBQD6AFMJeWgFxQBGYMJQA0UDlwBMvAUICU3alCWYm4nouWamAXigBGDUpKUkqzmimHNYqLoBEwQXavGAziQXXlDVa1lQAWgA%2BTBQYTy9rEBIYAFcQFH0rAGIoMnAQXjsAeT4AKxIAY3wwJngEEigAAyJSCkoAbT1RBydRYABdKsxXKBQwfEKqTj5KStY6WMqYMChYlCQwROMSCBIw3tqyKiaO0S36htawOw7ZZ01U6IA3EioSOl4AVRQAa36Ad0SAH1CYKxud0ozHKJHYflk1CAA

https://mypy-play.net/?mypy=latest&python=3.12&gist=31c8bdaa5521860cfeca4b92841cb3b7