Rollup merge of #22817 - jmesmon:result-or-type, r=huonw

Rollup merge of #22817 - jmesmon:result-or-type, r=huonw

 Changes .or() so that it can return a Result with a different E type
than the one it is called on.

Essentially:

    fn or(self, res: Result<T, E>) -> Result<T, E>

becomes

    fn or<F>(self, res: Result<T, F>) -> Result<T, F>

This brings `or` in line with the existing `and` & `or_else`

This is a
[breaking-change]
Due to some code needing additional type annotations.