RFC: https://amaranth-lang.org/rfcs/0019-remove-scheduler.html - [x] Deprecate `amaranth.lib.scheduler`: https://github.com/amaranth-lang/amaranth/pull/888 - [x] Remove `amaranth.lib.scheduler`: https://github.com/amaranth-lang/amaranth/pull/961 - [x] Changelog entry for removal