add "Deny All" Dns Resolver

[parkma99]

implement #329

[GlenDC]

Thanks, looks good.
Can you apply these changes,
and pull it onto your machine.

You might need to run just qa to quickly check if all passes.
It will also auto format in case there is some formatting to be done.

Should you not have just on your machine you probably can find install instructions
on https://just.systems/man/en/installation.html or for this instance you might get away to just check if cargo fmt --all doesn't give you new changes to commit.

If not too much to ask you can also squash your commits, but if not, also not ok, for now I'm still okay either way, it's what you want.

[GlenDC]

Suggested change

	pub struct DenyAllDns {}
	#[non_exhaustive]
	/// a [`DnsResolver`] implementation which
	/// denies all incoming DNS requests with a [`DnsDeniedError`].
	pub struct DenyAllDns;
	impl DenyAllDns {
	#[inline]
	/// Create a new [`Default`] [`DenyAllDns`].
	pub fn new() -> Self {
	Self::default()
	}
	}

[GlenDC]

Suggested change

	#[derive(Debug, Clone)]
	#[derive(Debug, Clone, Default)]