Add Send + Sync bounds to the sort_by function box, so that WalkDir can be Send + Sync. To make sure it doesn't regress, we should also add an assert_send and assert_sync macro (see the API guideline for inspiration) and test WalkDir, Iter and IterFilterEntry.
Relevant API Guideline
Add
Send + Syncbounds to thesort_byfunction box, so thatWalkDircan beSend + Sync. To make sure it doesn't regress, we should also add anassert_sendandassert_syncmacro (see the API guideline for inspiration) and testWalkDir,IterandIterFilterEntry.