Add function ABI and type layout to StableMIR

This change introduces a new module to StableMIR named `abi` with
information from `rustc_target::abi` and `rustc_abi`, that allow users
to retrieve more low level information required to perform
bit-precise analysis.

The layout of a type can be retrieved via `Ty::layout`, and the instance
ABI can be retrieved via `Instance::fn_abi()`.

To properly handle errors while retrieve layout information, we had
to implement a few layout related traits.

compiler/rustc_smir/src/rustc_internal/internal.rs

@@ -7,6 +7,7 @@
 use crate::rustc_smir::Tables;
 use rustc_middle::ty::{self as rustc_ty, Ty as InternalTy};
 use rustc_span::Symbol;
+use stable_mir::abi::Layout;
 use stable_mir::mir::alloc::AllocId;
 use stable_mir::mir::mono::{Instance, MonoItem, StaticDef};
 use stable_mir::mir::{Mutability, Safety};
@@ -460,6 +461,14 @@ impl<'tcx> RustcInternal<'tcx> for Span {
     }
 }
 
+impl<'tcx> RustcInternal<'tcx> for Layout {
+    type T = rustc_target::abi::Layout<'tcx>;
+
+    fn internal(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        tables.layouts[*self]
+    }
+}
+
 impl<'tcx, T> RustcInternal<'tcx> for &T
 where
     T: RustcInternal<'tcx>,