* 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`.