Rollup merge of #52674 - tinaun:patch-2, r=cramertj
Rollup merge of #52674 - tinaun:patch-2, r=cramertj

Impl Executor for Box<E: Executor>

removes the need for the compatibility lib between futures 0.1 and 0.3 to use a wrapper type to implement Executor for Box<Executor>

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