Use miette for reporting errors

This gives us errors with annotated context like this:

```
Error:
  × type error: Unknown variable 'x'
    ╭─[isle_examples/let.isle:24:1]
 24 │   (Lower (B.B z))
 25 │   (A.Add x y))
    ·          ┬
    ·          ╰── Unknown variable 'x'
    ╰────
```

cranelift/isle/isle/Cargo.toml

@@ -7,4 +7,5 @@ license = "Apache-2.0 WITH LLVM-exception"
 
 [dependencies]
 log = "0.4"
+miette = "3.0.0"
 thiserror = "1.0.29"