Auto merge of #121728 - tgross35:f16-f128-step1-ty-updates, r=compiler-errors

Add stubs in IR and ABI for `f16` and `f128`

This is the very first step toward the changes in rust-lang/rust#114607 and the [`f16` and `f128` RFC](https://rust-lang.github.io/rfcs/3453-f16-and-f128.html). It adds the types to `rustc_type_ir::FloatTy` and `rustc_abi::Primitive`, and just propagates those out as `unimplemented!` stubs where necessary.

These types do not parse yet so there is no feature gate, and it should be okay to use `unimplemented!`.

The next steps will probably be AST support with parsing and the feature gate.

r? `@compiler-errors`
cc `@Nilstrieb` suggested breaking the PR up in rust-lang/rust#120645 (comment)

Author: bors

src/common.rs

@@ -33,8 +33,10 @@ pub(crate) fn scalar_to_clif_type(tcx: TyCtxt<'_>, scalar: Scalar) -> Type {
             Integer::I64 => types::I64,
             Integer::I128 => types::I128,
         },
+        Primitive::F16 => unimplemented!("f16_f128"),
         Primitive::F32 => types::F32,
         Primitive::F64 => types::F64,
+        Primitive::F128 => unimplemented!("f16_f128"),
         // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
         Primitive::Pointer(_) => pointer_ty(tcx),
     }
@@ -61,8 +63,10 @@ fn clif_type_from_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<types::Typ
         },
         ty::Char => types::I32,
         ty::Float(size) => match size {
+            FloatTy::F16 => unimplemented!("f16_f128"),
             FloatTy::F32 => types::F32,
             FloatTy::F64 => types::F64,
+            FloatTy::F128 => unimplemented!("f16_f128"),
         },
         ty::FnPtr(_) => pointer_ty(tcx),
         ty::RawPtr(TypeAndMut { ty: pointee_ty, mutbl: _ }) | ty::Ref(_, pointee_ty, _) => {