Rollup merge of #80945 - sdroege:downcast-send-sync, r=m-ou-se
Rollup merge of #80945 - sdroege:downcast-send-sync, r=m-ou-se

Add Box::downcast() for dyn Any + Send + Sync

Looks like a plain omission, but unfortunately I just needed that in my code :)

aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust