Tracking issue for release notes of #129670: Make deprecated_cfg_attr_crate_type_name a hard error

[rustbot]

This issue tracks the release notes text for #129670.

• Issue is nominated for the responsible team (and T-release nomination is removed).
• Proposed text is drafted by team responsible for underlying change.
• Issue is nominated for release team review of clarity for wider audience.
• Release team includes text in release notes/blog posts.

Release notes text:

The section title will be de-duplicated by the release team with other release notes issues.
Prefer to use the standard titles from previous releases.
More than one section can be included if needed.

# Compatibility Notes
- The future incompatibility lint `deprecated_cfg_attr_crate_type_name` [has been made into a hard error](https://github.com/rust-lang/rust/pull/129670). It was used to deny usage of `#![crate_type]` and `#![crate_name]` attributes in `#![cfg_attr]`, which required a hack in the compiler to be able to change the used crate type and crate name after cfg expansion.

  Users can use `--crate-type` instead of `#![cfg_attr(..., crate_type = "...")]` and `--crate-name` instead of `#![cfg_attr(..., crate_name = "...")]` when running `rustc`/`cargo rustc` on the command line.
  
  Use of those two attributes outside of `#![cfg_attr]` continue to be fully supported.

Release blog section (if any, leave blank if no section is expected):

[Urgau]

@est31 What do you think about this compatibility notes?

# Compatibility Notes

- The future incompatibility lint `deprecated_cfg_attr_crate_type_name` [has been made into a hard error](https://github.com/rust-lang/rust/pull/129670). It was used to deny usage of `#![crate_type]` and `#![crate_name]` attributes in `#![cfg_attr]`, which required a hack in the compiler to be able to change the used crate type and crate name after macros have been expanded.

  Users must now use `--crate-type` on the command line when running `rustc` instead of `#![cfg_attr(..., crate_type = "...")]` and `--crate-name` instead of `#![cfg_attr(..., crate_name = "...")]`.

Compatibility Notes

• The future incompatibility lint deprecated_cfg_attr_crate_type_name has been made into a hard error. It was used to deny usage of #![crate_type] and #![crate_name] attributes in #![cfg_attr], which required a hack in the compiler to be able to change the used crate type and crate name after macros have been expanded.

  Users must now use --crate-type on the command line when running rustc instead of #![cfg_attr(..., crate_type = "...")] and --crate-name instead of #![cfg_attr(..., crate_name = "...")].

[est31]

I would write "Users can instead use" instead of "Users must now use" -- it's still entirely up to users what to do. They can also make separate crates where they include!() lib.rs.

"after macros have been expanded." after cfg expansion. Maybe also add "Use of the attributes outside of #![cfg_attr] is still supported.".

[Urgau]

Sure, updated with your suggestions and tweaked a bit the sentences.