For issue 53957: revise unit tests to focus on underlying bug of 23076.
For issue 53957: revise unit tests to focus on underlying bug of 23076.

Namely, this version focuses on the end-to-end behavior that the attempt to
create the UDP binding will fail, regardless of the semantics of how particular
DNS servers handle junk inputs.

(I spent some time trying to create a second more-focused test that would
sidestep the DNS resolution, but this is not possible without more invasive
changes to the internal infrastructure of `ToSocketAddrs` and what not. It is
not worth it.)

graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust