Update faerie, remove usage of failure (#591)

This commit removes the usage of the `failure` crate and finishes up the
final pieces of the migration to `std::error::Error` and `anyhow`. The
`faerie` crate was updated to pull in its migration from `failure` to
`anyhow` as well.

crates/debug/src/lib.rs

@@ -4,9 +4,9 @@
 
 use alloc::string::String;
 use alloc::vec::Vec;
+use anyhow::Error;
 use cranelift_codegen::isa::TargetFrontendConfig;
 use faerie::{Artifact, Decl};
-use failure::Error;
 #[cfg(not(feature = "std"))]
 use hashbrown::{hash_map, HashMap, HashSet};
 use more_asserts::assert_gt;