message: Rename `assert_uninit_valid` intrinsic
  It's not about "uninit" anymore but about "filling with 0x01 bytes" so
  the name should at least try to reflect that.
diff: @@ -713,7 +713,7 @@ fn swap(bcx: &mut FunctionBuilder<'_>, v: Value) -> Value {
  let res = CValue::by_val(swap(&mut fx.bcx, val), arg.layout());
  ret.write_cvalue(fx, res);
  }
  - sym::assert_inhabited | sym::assert_zero_valid | sym::assert_uninit_valid => {
  + sym::assert_inhabited | sym::assert_zero_valid | sym::assert_mem_uninitialized_valid => {
  intrinsic_args!(fx, args => (); intrinsic);
  let layout = fx.layout_of(substs.type_at(0));
  @@ -742,7 +742,9 @@ fn swap(bcx: &mut FunctionBuilder<'_>, v: Value) -> Value {
  return;
  }
  - if intrinsic == sym::assert_uninit_valid && !fx.tcx.permits_uninit_init(layout) {
  + if intrinsic == sym::assert_mem_uninitialized_valid
  + && !fx.tcx.permits_uninit_init(layout)
  + {
  with_no_trimmed_paths!({
  crate::base::codegen_panic(
  fx,
  