Rollup merge of #80850 - m-ou-se:rustc-builtin-macro-name, r=petrochenkov

Rollup merge of #80850 - m-ou-se:rustc-builtin-macro-name, r=petrochenkov

Allow #[rustc_builtin_macro = "name"]

This adds the option of specifying the name of a builtin macro in the `#[rustc_builtin_macro]` attribute: `#[rustc_builtin_macro = "name"]`.

This makes it possible to have both `std::panic!` and `core::panic!` as a builtin macro, by using different builtin macro names for each. This is needed to implement the edition-specific behaviour of the panic macros of RFC 3007.

Also removes `SyntaxExtension::is_derive_copy`, as the macro name (e.g. `sym::Copy`) is now tracked and provides that information directly.

r? ``@petrochenkov``