Better error when rustc fails to write output.

…ng#2910)

The main changes needed to make this migration besides a few method call
tweaks were:
1. Adapt `FunctionCtx` to cache information about the StableMIR version
of instance and its body.
- I also cleaned up how we were handling basic blocks which were
unnecessary.
2. Created a new ty_stable module that provide stable versions to
retrieve type information from StableMIR.
- I decided to keep these separate so it is cleaner for now. I foresee
that the type module will still rely on internal APIs for the next
little while, so separating them here made sense to me.
3. Since `Place` when retrieved from StableMIR body already comes
monomorphized, I modified the existing `codegen_place` to preemptively
monomorphize Place before converting it to a Stable version and invoking
`codegen_place_stable`.

### Call-outs

Leaving this as a draft for now since this still depends on the
following PRs to be merged into the Rust compiler:
  - rust-lang#118524
  - rust-lang#118516

---------

Co-authored-by: Adrian Palacios <[email protected]>

update autodiff install docs for nix