task: propagate attrs on task_local items to the generated items

[Arnavion]

Discovered while trying to add a #[allow] to try to work around #4836

That is,

tokio::task_local! {
	#[allow(clippy::declare_interior_mutable_const)]
	pub(crate) static TASK_LOCAL_LOGGER: env_logger::Logger;
}

... did not suppress the clippy lint, since the macro was not propagating the attr to the generated LocalKey

I did not find any indication in the commit and PR discussion that added task_local! that this was done intentionally, so it seems to have just been missed.

[Darksonn]

Thank you.