Auto merge of #65076 - tmandry:rollup-ka7nzb6, r=tmandry

Rollup of 11 pull requests

Successful merges:

 - #61879 (Stabilize todo macro)
 - #64675 (Deprecate `#![plugin]` & `#[plugin_registrar]`)
 - #64690 (proc_macro API: Expose `macro_rules` hygiene)
 - #64706 (add regression test for #60218)
 - #64741 (Prevent rustdoc feature doctests)
 - #64842 (Disallow Self in type param defaults of ADTs)
 - #65004 (Replace mentions of IRC with Discord)
 - #65018 (Set RUST_BACKTRACE=0 in tests that include a backtrace in stderr)
 - #65055 (Add long error explanation for E0556)
 - #65056 (Make visit projection iterative)
 - #65057 (typo: fix typo in E0392)

Failed merges:

r? @ghost