[stdlib] [SR-4005] Allow heterogenous comparisons in elementsEqual (#8045)

* [SR-4005] Allow heterogenous comparisons in elementsEqual

When a user is supplying a predicate to compare the type equivalence
isn’t required

* elementsEqualWithPredicate tests

Compares a string of a number with an integer value by using the
elementsEqualPredicate closure

* Update test expectations to use new sequence element types

* Update hardcoded test to reference sequence

stdlib/public/core/SequenceAlgorithms.swift.gyb

@@ -338,12 +338,14 @@ ${equivalenceExplanation}
   public func elementsEqual<OtherSequence>(
     _ other: OtherSequence${"," if preds else ""}
 %   if preds:
-    by areEquivalent: (Element, Element) throws -> Bool
+    by areEquivalent: (Element, OtherSequence.Element) throws -> Bool
 %   end
   ) ${rethrows_}-> Bool
     where
-    OtherSequence: Sequence,
+    OtherSequence: Sequence${" {" if preds else ","}
+%   if not preds:
     OtherSequence.Element == Element {
+%   end
 
     var iter1 = self.makeIterator()
     var iter2 = other.makeIterator()