[stdlib] Implement Equatable/Comparable sequence algos in terms predicate ones (#14758)

* Implement Equatable/Comparable sequence algos in terms predicate ones

* Remove IteratorSequence use

* de-gyb SequenceAlgorithms.swift

Author: airspeedswift

stdlib/public/core/CMakeLists.txt

@@ -110,7 +110,7 @@ set(SWIFTLIB_ESSENTIAL
   SipHash.swift.gyb
   SentinelCollection.swift
   Sequence.swift
-  SequenceAlgorithms.swift.gyb
+  SequenceAlgorithms.swift
   SequenceWrapper.swift
   SetAlgebra.swift
   ShadowProtocols.swift