* The `indexable_ptr_len` ZIR instruction now uses a `none_or_ref`
ResultLoc. This prevents an unnecessary `ref` instruction from being
emitted.
* Sema: Fix `analyzeCall` using the incorrect ZIR object for the
generic function callee.
* LLVM backend: `genTypedValue` supports a `Slice` type encoded with
the `decl_ref` `Value`.