Merge pull request #23197 from lorentey/numist/diffing-5.1

[5.1][SE-0240] Ordered Collection Diffing

Author: lorentey

stdlib/public/core/CMakeLists.txt

@@ -201,7 +201,9 @@ set(SWIFTLIB_SOURCES
   ${SWIFTLIB_ESSENTIAL}
   ### PLEASE KEEP THIS LIST IN ALPHABETICAL ORDER ###
   Availability.swift
+  CollectionDifference.swift
   CollectionOfOne.swift
+  Diffing.swift
   ExistentialCollection.swift.gyb
   Mirror.swift
   PlaygroundDisplay.swift