SE-0261: Identifiable Protocol

[jayton (Jens Ayton)]

To quote myself:

Move SwiftUI's Identifiable protocol and related types into the standard library

Could you summarize these discussions? In particular, I’m interested in the removal of identifiedValue, which would seem to make it impossible to implement Collection.identified(by:) (which seems generally useful) in terms of this protocol. Will SwiftUI have an additional abstraction over Identifiable?