Tracking issue for release notes of #139493: Explicitly export core and std macros

[rustbot]

This issue tracks the release notes text for #139493.

cc @Voultapher, @Amanieu, @petrochenkov -- original issue/PR authors and assignees for drafting text

See the forge.rust-lang.org chapter about release notes for an overview of how the release team makes use of these tracking issues.

Release notes text

This section should be edited to specify the correct category(s) for the change, with succinct description(s) of what changed. Some things worth considering:

• Does this need an additional compat notes section?
• Was this a libs stabilization that should have additional headers to list new APIs under Stabilized APIs and Const Stabilized APIs?

# Compatibility Notes
- [core and std macros are now imported via prelude, not via injected `#[macro_use]`](https://github.com/rust-lang/rust/pull/139493)
  This may raise a new warning ([`ambiguous_panic_imports`](https://github.com/rust-lang/rust/issues/147319)) on `#![no_std]` code glob importing the std crate.
  Both `core::panic!` and `std::panic!` are then in scope and which is used is ambiguous.

Tip

Use the previous releases for inspiration on how to write the release notes text and which categories to pick.

Release blog section

If this change is notable enough for inclusion in the blog post then this section should be edited to contain a draft for the blog post. Otherwise leave it empty.

Note

If a blog post section is required the release-blog-post label should be added (@rustbot label +release-blog-post) to this issue as otherwise it may be missed by the release team.

[Voultapher]

The # Compatibility Notes section is misleading, how about:

# Compatibility Notes
- [Standard library macros are now imported via prelude, not via injected `#[macro_use]`](https://github.com/rust-lang/rust/pull/139493)
  This will raise an error if macros of the same name are glob imported.
  For example if a crate defines their own `matches` macro and then glob imports that,
  it's now ambiguous whether the custom or standard library `matches` is meant and
  an explicit import of the name is required to resolve the ambiguity.
  One exception is `core::panic` and `std::panic`, if their import is ambiguous
  a new warning ([`ambiguous_panic_imports`](https://github.com/rust-lang/rust/issues/147319)) is raised.

[Voultapher]

@Amanieu, @petrochenkov I can't edit the issue description, please review and adopt the suggestion as sensible.