Remove "builtins." from output for overloads and builtins.None

[JelleZijlstra]

Part of #5072.

Overloads are probably the most common user-facing feature that still outputs "builtins" in error messages; this diff fixes them to use standard type formatting.

I also change builtins.None to None, since builtins.None is a syntax error. A comment claimed that we use builtins.None to distinguish the type from the value, but I don't think there are a lot of contexts where that confusion is likely.

[ilevkivskyi]

Thanks for cleaning this up! I would propose to change the error format to something like this:

• No overload variant of "f" of "A" matches argument type "B" if there is a single argument
• No overload variant of "f" of "A" matches argument types "A", "B", "C" otherwise.

(Note that quotes are used by some editor plugins to better highlight types/methods in error messages.)

[JelleZijlstra]

Yes, that would be better. What do you suggest for the case where the list is empty? (All overloads take at least one argument, but the user called f().) I suggest All overloads of "f" require at least one argument.

[ilevkivskyi]

Yes this makes sense.

[ilevkivskyi]

LGTM! Unless there are some objections, I will merge this soon.

[ilevkivskyi]

(also error message in tests needs to be updated)

[JelleZijlstra]

Oops, just pushed a commit fixing the two tests I messed up.