#[instrument] compatibility

[asomers]

The tracing crate provides a proc macro named #[instrument]. #[automock] currently fails to compile for structs or traits that contain such a method. For example, this will fail to compile:

use mockall::*;
use tracing::instrument;

#[automock]
pub trait Foo {
    #[instrument]
    fn foo(&self) -> u32;
}