Rollup merge of #101569 - m-ou-se:alloc-no-rexport-argumentv1, r=thomcc

Don't re-export private/unstable ArgumentV1 from `alloc`.

The `alloc::fmt::ArgumentV1` re-export was marked as `#[stable]` even though the original `core::fmt::ArgumentV1` is `#[unstable]` (and `#[doc(hidden)]`).

(It wasn't usable though:

```
error[E0658]: use of unstable library feature 'fmt_internals': internal to format_args!
 --> src/main.rs:4:12
  |
4 |     let _: alloc::fmt::ArgumentV1 = todo!();
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: add `#![feature(fmt_internals)]` to the crate attributes to enable
```
)

Part of #99012

library/alloc/src/fmt.rs

@@ -558,7 +558,7 @@ pub use core::fmt::Alignment;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::Error;
 #[stable(feature = "rust1", since = "1.0.0")]
-pub use core::fmt::{write, ArgumentV1, Arguments};
+pub use core::fmt::{write, Arguments};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{Binary, Octal};
 #[stable(feature = "rust1", since = "1.0.0")]

tests/pretty/issue-4264.pp

@@ -34,10 +34,11 @@
  ((::alloc::fmt::format as
  for<'a> fn(Arguments<'a>) -> String {format})(((<#[lang = "format_arguments"]>::new_v1
  as
- fn(&[&'static str], &[ArgumentV1<'_>]) -> Arguments<'_> {Arguments::<'_>::new_v1})((&([("test"
+ fn(&[&'static str], &[core::fmt::ArgumentV1<'_>]) -> Arguments<'_> {Arguments::<'_>::new_v1})((&([("test"
  as &str)] as [&str; 1]) as &[&str; 1]),
- (&([] as [ArgumentV1<'_>; 0]) as &[ArgumentV1<'_>; 0])) as
- Arguments<'_>)) as String);
+ (&([] as [core::fmt::ArgumentV1<'_>; 0]) as
+ &[core::fmt::ArgumentV1<'_>; 0])) as Arguments<'_>)) as
+ String);
  (res as String)
  } as String);
  } as ())

tests/ui/fmt/ifmt-unimpl.stderr

@@ -15,7 +15,7 @@ LL | format!("{:X}", "3");
  NonZeroIsize
  and 21 others
  = note: required for `&str` to implement `UpperHex`
-note: required by a bound in `ArgumentV1::<'a>::new_upper_hex`
+note: required by a bound in `core::fmt::ArgumentV1::<'a>::new_upper_hex`
  --> $SRC_DIR/core/src/fmt/mod.rs:LL:COL
  = note: this error originates in the macro `$crate::__export::format_args` which comes from the expansion of the macro `arg_new` (in Nightly builds, run with -Z macro-backtrace for more info)
 

tests/ui/fmt/send-sync.stderr

@@ -6,11 +6,11 @@ LL | send(format_args!("{:?}", c));
  | |
  | required by a bound introduced by this call
  |
- = help: within `[ArgumentV1<'_>]`, the trait `Sync` is not implemented for `core::fmt::Opaque`
+ = help: within `[core::fmt::ArgumentV1<'_>]`, the trait `Sync` is not implemented for `core::fmt::Opaque`
  = note: required because it appears within the type `&core::fmt::Opaque`
  = note: required because it appears within the type `ArgumentV1<'_>`
  = note: required because it appears within the type `[ArgumentV1<'_>]`
- = note: required for `&[ArgumentV1<'_>]` to implement `Send`
+ = note: required for `&[core::fmt::ArgumentV1<'_>]` to implement `Send`
  = note: required because it appears within the type `Arguments<'_>`
 note: required by a bound in `send`
  --> $DIR/send-sync.rs:1:12