Rollup merge of #100836 - hampuslidin:migrate-attr-crate-diagnostics, r=davidtwco

Migrate `rustc_attr` crate diagnostics

Hi!

This is my first PR to the rustc project, excited to be part of the development! This PR is part of the diagnostics effort, to make diagnostics translatable.

`@rustbot` label +A-translation

compiler/rustc_error_messages/src/lib.rs

@@ -34,6 +34,7 @@ pub use unic_langid::{langid, LanguageIdentifier};
 fluent_messages! {
     ast_lowering => "../locales/en-US/ast_lowering.ftl",
     ast_passes => "../locales/en-US/ast_passes.ftl",
+    attr => "../locales/en-US/attr.ftl",
     borrowck => "../locales/en-US/borrowck.ftl",
     builtin_macros => "../locales/en-US/builtin_macros.ftl",
     const_eval => "../locales/en-US/const_eval.ftl",