Stabilize const-calling existing const-fns in std

Fixes #46038

src/test/compile-fail/const-fn-feature-flags.rs

@@ -1,24 +0,0 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// Test use of const fns in std using individual feature gates.
-
-use std::cell::Cell;
-
-const CELL: Cell<i32> = Cell::new(42); //~ERROR not yet stable as a const fn
-    //~^HELP #![feature(const_cell_new)]
-
-fn main() {
-    let v = CELL.get();
-    CELL.set(v+1);
-
-    assert_eq!(CELL.get(), v);
-}
-

src/test/compile-fail/dropck_trait_cycle_checked.rs

@@ -13,8 +13,6 @@
 //
 // (Compare against compile-fail/dropck_vec_cycle_checked.rs)
 
-#![feature(const_atomic_usize_new)]
-
 use std::cell::Cell;
 use id::Id;
 

src/test/compile-fail/issue-17718-const-borrow.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(const_unsafe_cell_new)]
-
 use std::cell::UnsafeCell;
 
 const A: UnsafeCell<usize> = UnsafeCell::new(1);

src/test/compile-fail/issue-43733-2.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(const_fn, const_cell_new, const_unsafe_cell_new)]
+#![feature(const_fn)]
 #![feature(cfg_target_thread_local, thread_local_internals)]
 
 // On platforms *without* `#[thread_local]`, use

src/test/compile-fail/issue-7364.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(box_syntax, const_refcell_new)]
+#![feature(box_syntax)]
 
 use std::cell::RefCell;