More efficient deserialization of EntraIdErrorResponse

[chlowell]

For the error_description, mainly, you might rely on borrowing for less memory overhead if you're just trying to pick out a few things. We do that for ErrorResponseInternal and you can find more details at https://serde.rs/lifetimes.html#borrowing-data-in-a-derived-impl.

Originally posted by @heaths in #3302 (comment)