Rollup merge of #110766 - m-ou-se:fmt-rt, r=jyn514

More core::fmt::rt cleanup.

- Removes the `V1` suffix from the `Argument` and `Flag` types.

- Moves more of the format_args lang items into the `core::fmt::rt` module. (The only remaining lang item in `core::fmt` is `Arguments` itself, which is a public type.)

Part of https://github.com/rust-lang/rust/issues/99012

Follow-up to https://github.com/rust-lang/rust/pull/110616

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -296,7 +296,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                 diag_trait(&mut err, self_ty, tcx.require_lang_item(LangItem::Deref, Some(span)));
                 err
             }
-            _ if tcx.opt_parent(callee) == tcx.get_diagnostic_item(sym::ArgumentV1Methods) => ccx
+            _ if tcx.opt_parent(callee) == tcx.get_diagnostic_item(sym::ArgumentMethods) => ccx
                 .tcx
                 .sess
                 .create_err(errors::NonConstFmtMacroCall { span, kind: ccx.const_kind() }),