Rollup merge of #124067 - RalfJung:weak-lang-items, r=davidtwco

weak lang items are not allowed to be #[track_caller]

For instance the panic handler will be called via this import
```rust
        extern "Rust" {
            #[lang = "panic_impl"]
            fn panic_impl(pi: &PanicInfo<'_>) -> !;
        }
```
A `#[track_caller]` would add an extra argument and thus make this the wrong signature.

The 2nd commit is a consistency rename; based on the docs [here](https://doc.rust-lang.org/unstable-book/language-features/lang-items.html) and [here](https://rustc-dev-guide.rust-lang.org/lang-items.html) I figured "lang item" is more widely used. (In the compiler output, "lang item" and "language item" seem to be pretty even.)

compiler/rustc_resolve/src/lib.rs

@@ -1042,7 +1042,7 @@ pub struct Resolver<'a, 'tcx> {
     block_map: NodeMap<Module<'a>>,
     /// A fake module that contains no definition and no prelude. Used so that
     /// some AST passes can generate identifiers that only resolve to local or
-    /// language items.
+    /// lang items.
     empty_module: Module<'a>,
     module_map: FxHashMap<DefId, Module<'a>>,
     binding_parent_modules: FxHashMap<NameBinding<'a>, Module<'a>>,